Study Guide: Alternative Water Supply & Storage for Sanitary Plumbing (PDF)

Electrical Apprenticeship 30609.1 ed 1.0 Study Guide Demonstrate knowledge of alternative water supply and water storage for sanitary plumbing US 30609 | Level 4 | Credits 3 Name (First/Last): Unit standards Unit standard 30609 This study guide covers...

Electrical Apprenticeship 30609.1 ed 1.0 Study Guide Demonstrate knowledge of alternative water supply and water storage for sanitary plumbing US 30609 | Level 4 | Credits 3 Name (First/Last): Unit standards Unit standard 30609 This study guide covers: alternative water supplies for sanitary plumbing water storage systems for sanitary plumbing regulatory requirements as applied to alternative water supplies, and water storage systems for sanitary plumbing. The best way to use this Study Guide is: 1. Read through the following information step by step. 2. Where other resources are mentioned (such as websites), find those and read them as well. 3. Complete the Practice Exercises, then check your answers. Te Pūkenga acknowledges the content provided by the Ministry of Business, Innovation and Employment (including smarterhomes.org.nz), NZ Metal Roofing Manufacturers Inc (NZMRM), and The Plumbers, Gasfitters and Drainlayers Board to aid in the development of this resource. 30609.1 Contents Unit standards....................................................................................................................... 1 Legislation, Standards and Codes......................................................................................... 1 Legislation relating to alternative water supply systems................................................. 1 Building Codes and standards....................................................................................... 2 Alternative water supplies..................................................................................................... 3 Public water supply........................................................................................................ 4 Alternative water supply................................................................................................. 4 Activity 1............................................................................................................................ 4 Rainwater.......................................................................................................................... 5 Bore water......................................................................................................................... 9 Grey water....................................................................................................................... 11 Activity 2.......................................................................................................................... 14 Water quality and treatment............................................................................................. 15 Backflow protection...................................................................................................... 15 Water hardness and softness...................................................................................... 16 Water treatment methods............................................................................................. 16 Identifying pipework for non-potable supplies............................................................... 18 Water storage for alternative supplies.............................................................................. 19 Backflow prevention..................................................................................................... 21 Adequate water supply................................................................................................ 22 Activity 3.......................................................................................................................... 22 Water storage systems....................................................................................................... 23 Water for sanitary plumbing – residential..................................................................... 23 Water for sanitary plumbing – commercial and industrial buildings.............................. 23 Break tanks.................................................................................................................. 24 Flushing storage tank (internal header tank)................................................................ 25 External elevated reservoir.......................................................................................... 25 Emergency water supply................................................................................................. 27 Activity 4.......................................................................................................................... 28 Activity answers.................................................................................................................. 29  Page 1 of 31 Legislation, Standards and Codes Legislation relating to alternative water supply systems As you are already aware, work that we do as plumbers, gasfitters, or drainlayers needs to comply with relevant legislation. Many Acts, Codes and Regulations are of particular importance when it comes to alternative water supplies. Building Act 2004 The purpose of this Act is to provide for the regulation of building work, the establishment of a licensing regime for building practitioners, and the setting of performance standards for buildings. As well as complying with all aspects of the Building Act, you must use sound trade practice. This means that you are competent in what you do and use materials and processes that you know will work. This Act explicitly states in section 17 that all work must comply with the Building Code. These Codes set clear expectations of the standards buildings should meet. Health Act 1956 Plumbers are an important part of the healthcare system. The Health Act provides guidelines for water supplies and sanitary works. These services are vital for human health and wellbeing. Health and Safety at Work Act 2015 New Zealand’s key work health and safety law, also known as HSWA, places obligations and responsibilities on everyone in a workplace to take care of their own health and safety, and the health and safety of others. Plumbers, Gasfitters, and Drainlayers Act 2006; Plumbers, Gasfitters, and Drainlayers Regulations 2010 The Plumbers, Gasfitters, and Drainlayers Act and Regulations work together to determine who can legally install and maintain high risk systems such as sanitary plumbing and potable water systems. This includes both ensuring competency and regulating these trades. NZ Metal Roof and Wall Cladding Code of Practice Code of Practice This Code of Practice (COP) is published by NZ Metal Roofing Manufacturers Inc. It provides acceptable trade practice for the fixing of metal roof, wall cladding and accessories. The sections in the COP on roof drainage cover parts of the roofing system that are important for managing rainwater. 30609.1  Page 2 of 31 Building Codes and Standards These are just some of the clauses that may apply when installing water supply and water storage systems. This is also the case for standards. New Zealand Building Code Clause G10 Piped Services This Code gives performance requirements for piping systems, including marking pipes, isolation devices for repair, and the construction of systems to avoid contamination to piped services such as water. New Zealand Building Code Clause G12 Water Supplies Sets out the requirements of the Building Code in terms of protecting potable water from contamination, and other hazards/damage to property from incorrectly installed systems. New Zealand Building Code Clause G13 Foul Water This Code sets out requirements for the construction of plumbing systems, including sanitary fixtures and sanitary appliances which must be provided with adequate plumbing and drainage to the appropriate outfalls or system for treatment or storage. Part of this is protecting against infection or contamination of the water supply. AS/NZS 3500.1 – Plumbing and drainage part 1: Water services This Standard gives requirements for the design, installation and commissioning of cold water services and non-drinking water from the connection point to the point(s) of discharge. NZS 3604:2011 – Timber-framed buildings This Standard provides design details (drawings and tables) for building penetrations in floors and walls. You will often need to make these in building components to allow pipework to be installed. Work that follows NZS 3604:2011 automatically complies with Building Code requirements for some Clauses such as Structure. NZS 5807:1980 – Code of practice for industrial identification by colour, wording or other coding This Standard covers safety colours, warning signs and other indicators such as pipe labels which help to identify pipe contents. AS/NZS 1547:2012 – On-site domestic wastewater management The scope of this Standard is to cover the design and management of on-site domestic wastewater management systems. The reuse of grey water is covered, with some exclusions such as grey water diversion systems (see section C1.2.2). You must check with the local council first, as there is no national standard for grey water reuse in New Zealand. The sanitary plumbing connected to an on-site wastewater treatment system within the house must comply with the requirements of Building Code clause G13 Foul water. If the system is designed to AS/NZS 1547:2012, the Code requirements will be met. 30609.1  Page 3 of 31 Alternative water supplies Access to safe, clean water and safe and hygienic sanitation is recognised by the United Nations as a basic human right. With rising costs of water in some areas such as Auckland and the costs of new infrastructure and maintenance of existing water mains, there has been a push for the use of alternative water supplies. Most water in residential and commercial properties are supplied by the ‘mains’ public water supply. This is also known as drinking water, one of the three waters managed by the local council or territorial authority (drinking water, stormwater, wastewater). A typical building uses drinking-quality water (mains supply) for all water needs, even if it is used for tasks that do not need high quality water. The mains supply is processed and treated, and then will often be used for non-potable uses such as watering the garden or flushing the toilet. An alternative self-contained water supply that can be used for non-potable uses such as flushing toilets and washing clothes will reduce the amount of water being treated to a drinkable quality. Alternative supplies can also be treated for potable use. The diagram below summarises the different supplies. Water supply Public water supply Alternative water (reticulation supply network) (self-contained) Network Utility Private water Operator (NUO) collection Rivers, lakes, bore water, groundwater Rainwater etc Grey water Bore water (private supply) 30609.1  Page 4 of 31 Public water supply The public water supply is also known as the ‘reticulated water supply’ or ‘mains water’. The Ministry of Health provides guidance and standards such as the Health (Drinking Water) Amendment Act 2007, and the Drinking Water Standards for New Zealand 2005 (revised 2018) which ensures that all public water supplies are safe and palatable for the consumer. The typical supply is owned by the local territorial authority. They will manage the quantity of the supply and treat and test the water to make sure that it is safe. The pipeline which conveys water from the treatment facility throughout the region is called the water main. The pipe which branches off the water main to deliver water to each property is called the service pipe. The public water supply is provided by the Network Utility Operator (NUO). The network utility operator will supply water via the service pipe as far as each property’s boundary isolation valve (toby) and meter if fitted. At this point, it is the responsibility of the plumber to provide water to every outlet within the property without reducing the quality of the water. Alternative water supply Alternative water supplies are self-contained (private) water supplies that are not part of the public water supply. Three examples are rainwater, bore/well water and grey water. Alternative supplies can be used for garden irrigation, wash down and to supply sanitary fixtures and appliances. Depending on the quality of the alternative supply and the intended use, some filtering or treatment of the water may be required (see the section ‘water quality and treatment’ for more information). Using alternative supplies can reduce the reliance on and costs of mains water supply. There are some situations where public water supply is not available. For example, in rural areas, there may not be any alternative, as mains water is not accessible from their location. Due to distance, there may also be other problems such as low pressure from the mains outlet. With treatment, some alternative supplies may be used as a standalone supply for both potable and non-potable uses. According to G12, buildings provided with water outlets, sanitary fixtures or sanitary appliances must have safe and adequate water supplies. Whichever water supply is used (or combination of supplies), it must meet this functional requirement. Activity 1 1. What are the three waters managed by the territorial authority? 2. Is rainwater used as a public supply, alternative supply, or both? 30609.1  Page 5 of 31 Rainwater As plumbers, you may be asked to install rainwater harvesting systems. Rainwater harvesting systems are systems that collect the rainwater and store the water in tanks so that it can be used as a water supply. Rainwater can be collected and used as either a non-potable or potable water supply, depending on the design of the system and the quality of the collected water. Collecting Rainwater can be collected from roofs and stored for use. Gutters, internal and external (spouting) are a channel used to collect rainwater being discharged off a roof. External gutters or spouting are slightly graded (sloped) to prevent ponding and direct the water to downpipes which take the collected water to the water tank. The size of the gutter must be adequate to cope with the size (plan area) of the roof and the expected rainfall for the location of the installation without overflowing under normal conditions. New Zealand Building Code clause E1 provides graphs, tables and other information required to size gutters, downpipes and overflows. To keep the rainwater as clean as possible you need to make sure that the roof and pipe materials are suitable, the catchment area (roof and gutters) are free of leaves and debris, and that the system is regularly cleaned/maintained. You could recommend the installation of mesh and filters such as gutter guards or screens to reduce the amount of debris entering the system and the likelihood of blockages in the pipework. Gutter screens Filter screen for downpipe Depending on the intended use of the stored rainwater, some treatment or filtering may be required. Local councils/TAs will often have legislation around this, especially when the water will be used as a potable supply. 30609.1  Page 6 of 31 Although anybody is permitted to install and maintain external gutters or spouting and the downpipes connected to them, this work is often completed by plumbers. Depending on where the downpipe terminates, the downstream system may or may not require a licensed tradesperson to complete the work. For example: If the downpipe is going to discharge into a stormwater drainage system, then a licensed drainlayer will be required to complete that downstream work. More information on the installation of stormwater drainage systems is available in the stormwater 30577 study guide. If the downpipe is going to discharge into a rainwater storage tank (harvested) to supply water only for irrigation (garden hose tap), then any competent person may complete the installation. If the downpipe is going to discharge into a rainwater storage tank (harvested) that will be used to supply any sanitary fixtures either as a potable or non-potable water supply, then the installation must be completed by a licensed plumber. Storing The selection of material for the storage tanks is also critical as the water will be in contact with this material for long periods of time. The tank must be made from a material that will not affect the water by releasing chemicals that will make the water unsafe, look unpleasant, or affect taste. The tank material must be strong enough to withstand the weight of the water stored and the pressure that creates. The material should also be of a colour/thickness that will not allow the sunlight through. If sunlight is able to enter the tank, it will allow plants (moss, algae, etc.) to grow inside the tank, which will have an undesired effect on the quality of the water. The material should also be smooth to allow for easy cleaning. Where possible, consider installing the tank in the ground. This keeps the water cooler and fresher and reduces the chance of bacteria multiplying. The surrounding soil will also support the weight of the tank when filled with water, and assist in keeping sunlight out. The minimum requirements for different types of rainwater tanks are listed below. 1. Polyethylene Tanks – Certified to AS/NZS 4766 (Australian Standard – Polyethylene Storage Tanks for Water). 2. Steel Tanks – Tank designed by suitably qualified Engineer and constructed using materials certified to AS/NZS 2180. 3. Concrete Tanks – Certified to AS/NZS 3735 (Australian Standard – Concrete Structures Retaining Liquids). 30609.1  Page 7 of 31 Rainfall in most areas of New Zealand is changeable, and it is important to ensure that the water supply for a building will be adequate (for example over the summer months or during a drought). Sanitary fixtures must have a constant supply of water to guarantee the building remains hygienic and usable. There are several ways to ensure the supply is maintained, such as having a tank large enough to store water to last through a dry period, and/or access to a top-up supply. A top-up supply could be provided by a bore, water truck delivery or a connection to the network utility operator’s (NUO) water main. An NUO connection is likely to be supplied at a restricted flow rate (trickle feed) of approximately 1.8m³ per day. If a collected rainwater system is to be topped up, adequate backflow prevention must be included in the system. Untreated rainwater cannot be allowed to enter the top-up supply source. Information on how this can be achieved can be found in the water quality and treatment section or the backflow study guide (30598). Water storage tanks must also be fitted with an overflow to dispose of excess water (if for example, it continues to rain) once the tank is full. This overflow must discharge to the territorial authority’s (TA’s) stormwater system, a soak pit or some other suitable outfall. See E1 for more information on suitable outfalls. Using One example of an urban development that utilises rainwater is Hobsonville Point in Auckland. The development is designed to be as environmentally friendly as possible. One of the requirements when getting a consent to build in the area (on top of the building code requirements) is that “dwellings are served by rain tanks sized to supply 75% of water used in household toilets, laundries and gardens.” Rainwater can also be used for potable supply, but in some situations only if there is suitable filtering and treatment (this often depends on the TA, which may require testing, filtering, or treatment). If the quality of the rainwater cannot be guaranteed, it should not be used for drinking, cooking, or bathing. Suitable uses for untreated water include garden irrigation, washdown, WC flushing or laundry/clothes washing. All water supply systems must be designed to prevent backflow occurring and contaminating the water. This is a greater risk when the building is supplied with water from different sources or different qualities. Special care should be taken at outlets that are fitted with mixing valves, where the valve receives water from two different systems (e.g., NUO Mains and rainwater). This is most likely (but not limited to) laundry tubs and clothes washing machines where there may be a non-potable cold water and a potable hot water supply. There are many options that can be used to manage the backflow risk in these types of situations, including: installing a backflow prevention device where the hot water is connected to the mixer or washing machine suppling the laundry tub through two separate taps so that no mixer is installed supplying only non-potable cold water to the tub and washing machine and have no hot water supply to the laundry, or connecting the laundry to both potable cold and hot water. 30609.1  Page 8 of 31 The Building Code sets clear, performance-based expectations of the standards buildings should meet. The building codes are the best places to find information on areas such as backflow (G12/AS1), and sizing components for rainwater systems (E1/AS1). Rainwater storage system for household use 30609.1  Page 9 of 31 Bore water Similar to collected rainwater, bore water has been used for decades as a primary source of potable water (when treated). In recent times this is more common for rural properties not served by a reticulated water supply. In some areas of the country however, whole towns are supplied from bores controlled by the local territorial authority. Collecting If the homeowner is installing a private bore, then they will need a bore permit before drilling, and may require a resource consent depending on the amount of water that will be taken. A specialist drilling company will install the bore, then the plumber’s job is to install the lines from the bore to the house. As it is a technical area, the best thing to do if you are called in by someone setting up such a system is to work with a specialist firm to address the specific requirements. For private supplies, it is important that the homeowner protects the supply point and checks the area regularly for damage and makes repairs. Regular testing of private bore water supplies should be encouraged (regular testing is mandatory for public bore supplies). Bores can become contaminated for many reasons: cracks opening up within the ground due to dry weather or earthquakes, this can allow contaminated surface water to enter the bore without being filtered through the surrounding soil animals could gain access to the bore water supply and infect the water with their faeces or carcasses pipework between the bore and the point of supply becoming damaged, or a cross-connection within the pipework system could allow pollutants to enter the water supply It is possible for people who have lived for long periods in a dwelling supplied by bore water to develop an immunity to low levels of contamination in that supply, leaving any visitors or temporary occupants susceptible to illness from the same water. Therefore, it is safer to install a filter or treatment system to the water supply or limit the use of bore water to supply non-potable outlets only, reducing the load on the potable supply. It is important to consider the pipe material for the installation. Bore water can be high in minerals (hard water) and could corrode the pipework and cause problems. Although copper, in general, has good corrosion resistance, this depends on the environment. Highly acidic or alkaline conditions, either from the soil (if buried) or from the water can cause corrosion, so local pH levels should be checked before using copper pipes. 30609.1  Page 10 of 31 Storing Storage requirements for bore water are similar to rainwater. If a system is to be used in conjunction with a network utility operator’s supply, adequate backflow prevention must always be included in the system. Untreated bore water cannot be allowed to enter the network utility operator’s (NUO) water main. See the section on water storage for more information. Using In 2016 the bore supplying 15,000 residents of Havelock North on the east coast of the North Island became contaminated. 5,500 people became ill, 45 of which were hospitalised, and four people died. Following the outbreak in Havelock North, territorial authorities have become much more aware of their responsibilities in ensuring their residents are supplied with clean, safe, potable water. To meet this requirement, many are now routinely testing and treating their bore water supplies to prevent another similar situation occurring. Water from region to region will always have noticeable differences in taste. For areas utilising bore water, there is a possibility of ammonia, nitrates, iron, and calcium as well as other naturally occurring minerals being present. Most of the undesirable contaminants or minerals can be removed or neutralised by filtering, exposure to UV light, and/or boiling or by adding other beneficial minerals to the supply. These treatment options can be used at both regional water treatment facilities and private water supplies (the section on water quality and treatment has more information). Rural or country properties are more likely to use bore water to supply their house as reticulated water mains are seldom available in these areas. The only way to know if the bore water supply is safe is through regular laboratory testing. The local council or public health unit is a good source of information regarding testing. 30609.1  Page 11 of 31 Grey water Grey water is a term relating to waste water from sanitary fixtures and appliances that does not include any human waste. Waste water from fixtures such as basins, baths, and laundry tubs are generally acceptable to collect as grey water for reuse. Waste from WC pans and urinals, for example, cannot be reused due to the high health risks associated with human waste. Kitchen waste is also unsuitable to be collected as grey water as it is high in fats, oils and grease (fogs). Reusing grey water can reduce the amount of water needed from the potable supply system, however because of the low quality of the water it can only be used for garden irrigation. If filtered, treated to remove odours, and disinfected it can be possible to use grey water for toilet flushing. A building consent is required to collect grey water for reuse on the garden or for toilet flushing. Collecting grey water Managing the collection of grey water can be difficult and requires effort from the homeowner/occupier. Laundry tubs and clothes washing machines are generally acceptable fixtures/appliances to collect grey water from, however, if soiled clothing or nappies are being cleaned the discharge will contain human waste and should not be collected but diverted to the foul water drain. The first rinse from a clothes washing machine is also very high in detergents which could damage plants and soil in the garden so may also need to be diverted to the foul water drain. Baths and showers (particularly of small children) also have the potential to be contaminated with human waste. People wanting to collect grey water for reuse need to be vigilant to ensure the water collected is of a useable quality, even if it is only used to provide water for irrigation. In addition to making sure no human waste makes its way into the grey water system, consideration needs to be given to the type of soaps and detergents being used. Cleaners low in salts, boron and other chemicals should be chosen. It is advisable that if a member of the household is unwell, all waste should be diverted to the foul water system to reduce the possibility of viruses and disease being spread to others. A filtering system to prevent lint and hair will need to be included in the design and cleaned out regularly to prevent blockages. Storing grey water Grey water should be used as soon as possible and must be used within 24 hours of being created. The high levels of bacteria, skin cells, and detergents can cause the water to become unsafe and smelly if stored for a prolonged period of time. An overflow to the foul water drain must be provided for times when more grey water is being created than is able to be absorbed by the garden. The ability to divert grey water directly to the foul water drain must also be incorporated into the system for times when waste that will damage the garden is being produced. 30609.1  Page 12 of 31 Using grey water As stated above, when grey water is being used for garden irrigation, it must be used with 24 hours of being created. The grey water must also be applied to the garden around 100 mm below ground level, and must not be applied in large quantities that could cause ponding on the surface. This reduces the risk of people being exposed to the bacteria in the grey water. If the soil is already waterlogged, for example from recent rain or previous doses of grey water more grey water should not be applied as it will not be able to soak into the earth and will damage the plants and soil structure. Grey water should not be used to water plants that are intended to be consumed, such as vegetable or herb gardens. Some plants, especially young seedlings, do not cope well with the high alkalinity of grey water. Plants that are able to withstand high pH water and soil should be chosen. Adding compost, mulch and gypsum can help to balance the nutrients in the soil and lower the pH. Grey water pipework should be flushed with fresh water for a few minutes on a weekly basis to clear the pipework and rinse the soil and plants. Dividing the garden into sections to allow different areas to rest and recover from doses of grey water is also beneficial. Garden divided into sections Because grey water is not suitable to be stored, it must be treated to reduce harmful bacteria to an acceptable level, if it is to be used for WC flushing where it may need to be kept in a tank or cistern for an extended period of time. Commercial buildings such as hotels and corporate buildings could reduce their water consumption and therefore their supply costs drastically by reusing bath/shower water, hand basin and laundry water to flush toilets or water gardens. Grey water recycling system 30609.1  Page 13 of 31 A grey water study was conducted in 2019 by BRANZ (Building Research Association of New Zealand) and ESR (Institute of Environmental Science and Research). The research covered the water quality of grey water in 10 properties (8 residential, two commercial) and talked to councils to see how they viewed grey water use. The findings of the study were that the potential risks for contamination are dependent on: the source and installation of the systems the occupant/customer lifestyle and customs. Bacteria numbers will depend on the source of the grey water. Some water sources can be higher in bacteria based on the customer (such as bathwater from small children). There is no national guideline for grey water reuse in New Zealand, and councils are divided in their opinions of grey water. The ability to install and gain consent for a grey water system depends on the council/area. Some policies do not mention grey water at all or only talk about grey water in the context of large rural sites or blackwater (discharge containing human waste) storage designs that combine grey and blackwater together. For this reason, most councils currently do not allow grey water recycling that incorporates new designs, such as systems that do not require storage. Other councils encourage new and ecological solutions for water use. The Kāpiti Coast District Council has guidelines for the use of rainwater and grey water. For houses built after 2008, the council requires all homes in urban areas to install on-site supplies for toilet flushing and outdoor uses. For houses built before 2008, they offer a funding scheme for installing an on-site non-potable supply. Rainwater and bore water are still more likely to be used for a non-potable supply in this area. Other parts of the world have used grey water effectively when dealing with severe droughts. In Cape Town, South Africa, there was a severe shortage of water from 2015 to 2018. The dam levels declined, with the worst of the drought being experienced during mid-2017. Significant water restrictions were required, and one of the solutions was to encourage grey water or rainwater for toilet flushing and to ban all outdoor or non-essential use until dam levels rose. Grey water conclusion There is a place for grey water reuse. Being high in nutrients, it can reduce the need for fertilisers and reduce the amount of potable and wastewater needing to be treated. Disposing of grey water to gardens can help lessen the load on sewage treatment plants and on-site sewage treatment systems. Other factors to consider are the property owner’s willingness to choose their detergents and soaps carefully, to keep up to date with weather activity in the area, flush pipework and clear filters regularly, and apply compost and mulch to the garden as well as selecting plants suitable for the type of soil being created. Checking for boggy soil, changes in plant growth rates, wilting foliage or the presence of pests (rats, cockroaches and other vermin) needs to be carried out as they are signs that the system is not working correctly. There are electronic systems available to help manage the collection and disposal of grey water automatically or at the flick of a switch. At present, these systems are expensive and not commonly installed. 30609.1  Page 14 of 31 There are no national rules for the reuse of grey water in New Zealand. Some territorial authorities have or are developing guidelines regarding collecting and using grey water. At this stage, because New Zealand usually has an adequate supply of high-quality water available, and due to the potential risks of contamination (even in disciplined households where all of the correct procedures are followed), territorial authorities are cautious, and generally the reuse of grey water is not encouraged. Activity 2 Read through the scenarios for each household, and recommend which alternative water supply would work best from rainwater, bore water or grey water. You may choose more than one alternative water supply if you can provide reasons for both. You must provide at least two reasons for your answer. 1. The customers are a family of 6 who live on a small lifestyle block right on the edge of the city. They currently use mains supply but are sick of paying high water bills. They are looking for a low maintenance system to reduce their water bill and supplement the mains supply water by supplying all of their sanitary plumbing needs. Their largest water use is the bath/shower, as they have two young children and two teenagers. Best system: Reasons: 2. A couple wants to build a new ‘eco’ house in a rural area about an hour from Christchurch. They would like to minimise their impact on the environment by getting their water from alternate sources. They are not scared of high maintenance or large set up costs. Their goal is to create a system that is as sustainable as possible. Best system: Reasons: 30609.1  Page 15 of 31 Water quality and treatment Keeping private water supplies pure begins at the catchment area. For example, for rainwater, installing a mesh screen in guttering will prevent large impurities from entering the storage tank. For bore water, fences and signage will help prevent contaminants from entering the water source. When water is stored in the tank, any silt and organic matter will settle at the base. The tank must be made out a suitable material to prevent contamination and algae growth. The water at this stage may be potable, but it is recommended that further purification such as filtering or treatment takes place prior to consumption. It's important to think about all aspects of the water supply system. Safe setup and regular maintenance of the system is the easiest way for the customer to maintain their water quality. Treatment may be required if the water contains any unwanted contaminants, especially if it is to be used as a potable (drinking water) supply. Local councils/TAs will often have legislation around this, including testing new water supplies to make sure it is safe to drink. Foreign matter Not only does foreign matter affect the appearance, taste and odour of water, it can also harm a person’s health. For example, if industrial or agricultural waste were to enter a water source, this foreign matter could be hazardous. Disease producing organisms Disease-producing organisms may be transmitted through water. These organisms can enter a water source via animals, humans, plant life or fungi. If an animal defecated upstream of a water catchment area, diseases like Escherichia coli (E-coli) could be contracted if the water is consumed without prior treatment. Backflow protection Where a water system is connected to pipework supplying water from another source (e.g. town water, bore water, etc.) you must ensure water from both systems cannot backflow from one into the other. The suitable prevention method varies depending on the potential risk the cross-connection could have on people’s health. Depending on the situation and the type of device required and installed, the customer or building owner may need to organise for the device to be tested every year. This is to ensure the backflow protection is operating correctly. More information relating to cross-connection and backflow is available in New Zealand Building Code Clause G12/AS1 Section 3.1 and the backflow study guide (30598). 30609.1  Page 16 of 31 Water hardness and softness Water’s hardness and softness are due to the quantity and type of minerals present in the water — calcium and magnesium. Water that is considered ‘soft’ will have lower mineral concentration. Water hardness can be checked by having the water tested to determine how many milligrams of each different mineral is present in a litre of water. Hard water also tends to raise the pH level of the water, so a simple pH test can be helpful. pH measures the amount of hydrogen ion activity in a substance. The pH scale is relative and goes from 0 to 14. 0 is the lowest, and most acidic, pH level 7 is neutral, and 14 is the highest and most alkaline pH level. Pure water is seen as the ‘neutral’ pH — the pH for pure water at 25°C is close to 7.0. Solutions with a pH less than 7 are said to be acidic, and solutions with a pH greater than 7 are said to be basic or alkaline. Acid water can cause metal pipe materials to corrode. In some water supply areas, the acidity of the water supply will require materials which will not corrode. Supplying hard water to a property can also cause premature failure of pipework and fittings. This is because water which is high in minerals could corrode the pipework and cause problems. Hardness of water has an effect on personal and household washing. Hard water does not allow soap to readily form a lather, and therefore, more soap is required for cleansing. Hardness producing salts do not usually make water non-potable (non-drinkable) however, the hardness level can be reduced by boiling or by on-site water treatment. Water treatment methods There may not be clear guidelines for water treatment for private supplies; this may depend on the local council/territorial authority (TA). However, the NZBC still applies, and people must be safeguarded from illness caused by contaminated water. Backflow prevention and proper system design are still required. There are strict standards for drinking water. When water is for sanitary plumbing use (bathing, showering, etc.), it must also be safe. Toilet flushing and garden irrigation can use non-potable (non-drinking) water. For example, water from an alternative water supply such as untreated rainwater could be used for showering without any treatment. According to the HealthEd website, the main requirements of bathing/showering/cleaning water is that it must be biologically safe. The requirements for water used for toilet flushing are that it is not discoloured or stain-causing. In some cases, territorial authorities will have guidelines or requirements for water quality. For alternative supplies like bore and rainwater, this includes treating contaminants and verifying that the water is safe (and potable if required). This may require chemical addition, distillation, filtration, straining or treatment with UV light. 30609.1  Page 17 of 31 Chemical addition To treat water through adding chemicals, it’s important to talk to an expert first. The HealthEd website lists treatment methods based on the water issue, including chemical treatments. Although uncommon in a domestic situation, water may be treated by adding chlorine to disinfect and lower the numbers of any bacteria present to safe levels. For example, in public water supplies, chlorine is often added to remove contaminants that can come from a variety of sources. Distillation or boiling Distillation is the boiling of water to filter out impurities by evaporation. Distillation effectively removes bacteria, organic chemicals, lead, nitrates and pesticides from water. Small scale plants are sometimes used in homes and laboratories. It is recommended that water is boiled for 10 minutes. Boiling is helpful in emergency situations when it is unclear what contamination may be present and how safe the water is. It is a very reliable method of purification, but it is both time and energy-consuming. It is usually only used in commercial or emergency situations. Filtration/straining Filters help remove impurities from the water. This may include a basic line strainer that will remove any large solid particles from the water supply, or, in some installations further filtering to take out microscopic particles may be required or simply preferred by the property occupier. These filters are installed on the pipework between the tank and the outlet(s) that require this level of cleanliness. They are available in many different sizes to achieve the flow rates required for the number of outlets they serve. Filters are also available with different ratings to provide the level of treatment desired. The pore size is expressed in microns (one micron is 1000th of a millimetre). A 30 micron sediment filter is used to remove small solids that may be floating within the water. The water can then be passed through further filters with ratings ranging from 20 micron down to 5 micron and carbon filters to reduce or remove any odours, colours or bacteria. In-line filters are easily maintained and relatively cost-effective. Small domestic filters should be replaced when the flow rate drops to unacceptable levels or at specific time intervals. The replacement schedule will vary depending on the type of filter, how many litres of water has been passed through the filter and the initial quality of the water being supplied. UV (ultraviolet light) treatment Sometimes referred to as UV filters, these can also be added to improve water treatment. This treatment works by shining UV light (which kills any bacteria present) into the water as it passes through the device. Care must be taken to ensure the correct size and design of filter is installed. The UV light must be able to reach all of the water as it flows through the filter, otherwise there is a chance that the water in the centre of the pipework can flow through untreated. 30609.1  Page 18 of 31 Identifying pipework for non-potable supplies Pipelines need to be identified in certain circumstances by label and/or colour. Section 4.3 of Clause G12 states that where a non-potable water supply is reticulated around the building, the potable and non-potable pipelines shall be identified in accordance with NZS 5807 Code of practice for industrial identification by colour, wording or other coding. Suppliers will have label designs based on this standard. Another alternative solution is AS/NZS 3500.1, which states that the colour of non- drinking water pipework should be purple/lilac and gives a small range of possible shades. The markings should still follow NZS 5807. On most large industrial and some commercial sites identification is mandatory. Some sites may have their own specific coding for identification of their services. This identification is required to assist when isolating and maintaining sections of pipework. Correctly identifying pipework and turning the appropriate water supply off before cutting through the water pipe avoids potential danger or damage to property and harm to people. In domestic situations, pipeline identification is not required unless the building has both potable and non-potable water supplies. In this situation, pipework systems need to be identified. Signage is required at all outlets supplied with non-potable water. Users must be warned that the water is not suitable for drinking by installing the sign shown below at each outlet. The sign must be a minimum of 100 mm high and positioned so it will not be obscured when the outlet is used. NZBC F8 signs (F8/AS1) 30609.1  Page 19 of 31 Water storage for alternative supplies Alternative water supplies are housed in large capacity tanks or groups of tanks. The installer needs to be aware of the intended use of the stored water and whether any other water supplies will be connected to the tank. It is important that all collected water is of the required quality and that any cross-connections between different water supplies are avoided or managed correctly. Where possible the inlet and outlet of a water storage tank should be on opposite sides to ensure the water flows through the tank. This lessens the likelihood of pockets of water remaining in the tank for extended periods of time and becoming stagnant. Stagnant water can allow bacteria to grow, making the water contaminated and/or smelly. The water supply outlet should also be located above the base of the tank to prevent any settled dirt (sludge) on the base of the tank getting into the water supply pipework. Tank diagram supplied by the PGDB Another option is to install the tank outlet with a float and flexible connection. This will hold the pipe slightly below the water level to prevent any floating debris from the water surface and any sediment from the base of the tank entering the property’s potable water supply system. Any aged water will be disposed of through the overflow as it is extended to the base of the tank. Tank diagram supplied by the PGDB 30609.1  Page 20 of 31 Some New Zealand communities use dual water sources. The two sources are usually rainwater (reasonable quality but not always available) and bore water (possibly poorer quality but usually available). One storage tank can be used to receive water from both sources, with a float valve (ball cock) controlling the supply from the bore. Rainwater fills the tank and is used until a period of dry weather occurs. When this happens and the water level falls, and the float valve opens, water from the bore will enter the tank. As the bore water flows into the tank, the pressure in the pipework will drop, activating a switch to turn the bore pump on to maintain the flow. At times rainfall will produce more water than required, and the tank will be full. In these cases, the excess will need to be disposed of through an overflow to a suitable outfall. The overflow can be designed to take water from near the bottom of the tank. This is to discharge what is likely to be the oldest water, and it is possible that the overflowing water may carry some of the sediment from the base of the tank through to the outfall, keeping the tank cleaner. Tank diagram supplied by the PGDB (modified) 30609.1  Page 21 of 31 Backflow prevention As previously mentioned in the water quality section, you must ensure water from both systems cannot backflow from one into the other. The diagram below shows a rainwater storage tank with two options for supplementary water supply. Other valves and components have been left off the diagram to highlight the backflow prevention requirements. For Option A where the supplementary water supply is providing top up water to keep the storage tank full, backflow prevention is usually achieved by including an airgap. An airgap is a vertical space between the supplementary water supply outlet and the overflow level of the tank. This ensures excess water will overflow from the system before it reaches the level of the supplementary supply connection. Option B shows the supplementary supply being connected directly into the house water supply pipework. With this option a backflow prevention device must be installed to ensure the stored rainwater cannot enter the pipework from the supplementary water supply, and another backflow prevention device is installed to ensure water from the house and the supplementary water supply cannot backflow into the storage tank. Depending on the type of device required and installed the customer may need to organise for the device to be tested every year to ensure it is operating correctly. More information relating to backflow prevention is available in G12/AS1 Section 3.1 and in the backflow study guide (30598). Two options for backflow prevention 30609.1  Page 22 of 31 Adequate water supply A house must always have an adequate supply of water to meet the needs of the household. This includes both potable and non-potable uses. Some territorial authorities will tell you what the minimum acceptable storage tank size is, but have a chat with your customer, asking questions such as: How many people are going to be living there, and what are their water use habits? (If it’s a rain harvesting system) What is the rainfall in summer like? Are other people in the area having to organise water deliveries in the summer? Give them the option to consider having a tank bigger than the minimum required. This will lessen the likelihood that they run out of water which, as well as being inconvenient, requires them to purchase water from the NUO or water truck delivery companies. The additional costs of a larger tank may be more economical over time. There are several ways to ensure the supply remains adequate when the alternative water supplies are not keeping up with demand, for example, during drought periods for rainfall. 1. Make sure that the storage tank is large enough to contain a sufficient amount of water for the expected usage. 2. Organise water delivery by truck to fill the tank when the water level is low. 3. If available, connect the tank or the outlets to a secondary alternative water supply to fill the tank or provide water to the outlets when the tank is empty. One example is a rainwater supply with a backup bore water supply. 4. If available, connect a water supply from the ‘town water’ reticulated water main. When available, this is usually achieved by installing a float valve (ball cock) that will open and close as required to allow water to enter the tank. The float valve will provide a low flow rate so that the pressure in the water main does not drop too much, and the property does not use excessive amounts of town water. The town mains water supply is likely to be metered, and an invoice for the amount used will be charged to the property owners. 5. In some areas, a town supply is readily available and a tank is not necessary. However, the property owners may choose to install a storage tank system as in 4. to keep the cost of metered water to a minimum. Activity 3 1. G12 states that “buildings provided with water outlets, sanitary fixtures or sanitary appliances must have safe and adequate supplies.” Give one way of making sure that a house supply is safe, and one way of making sure it is adequate. Safe: Adequate: 30609.1  Page 23 of 31 Water storage systems G12 states that a water supply system is the pipes, fittings and tanks used or intended to be used for the storage and reticulation of water from a water main or other water source, to sanitary fixtures, sanitary appliances and fittings within a building. This section will mainly focus on water storage systems for sanitary plumbing, but will also cover other areas such as reservoirs and emergency use. Water for sanitary plumbing – residential Water storage systems for sanitary plumbing in residential buildings has been discussed in the previous section on water storage for alternative supplies. If water mains are used, then there may not be a need to store water on a residential property as there will be an adequate supply. For all systems connected to sanitary plumbing, backflow prevention must be included in the system design. See ‘water storage for alternative supplies’ for more information. Water for sanitary plumbing – commercial and industrial buildings Commercial and industrial buildings have the same requirements as residential supplies (such as backflow protection), but very different water supply requirements. Some buildings use a system that is custom-made for their requirements. Due to the size and nature of commercial and industrial buildings, the water supply system may need additional installations to supply enough water to meet the demand required. It will be based on the network utility’s requirements (water mains), and also the water demand of the building. Water can be supplied to a building by one of two methods, the direct or indirect system. Modifications can be made to these systems to suit specific needs. Direct system The direct system effectively runs a water supply straight from the water main through the building, supplying water to all outlets. This system is not suited to high-rise structures as the pressure will gradually decrease as the supply rises. Water supplied at 300 kPa will push water up to 30 metres, or the equivalent of a 10 storey building, however there will be no flow. The design of any direct supply system should ensure there is a ‘residual pressure’ (remaining pressure) of 5 m or 50 kPa. When water is drawn from all floors simultaneously, the total demand may reduce the flow, preventing water from reaching the uppermost floors. 30609.1  Page 24 of 31 Benefits of the direct system include: It is a cost-effective system as there is less pipework involved. Smaller diameter pipes may be used. All outlets will be supplied with potable water. The supply pressure may be affected if a large draw off (fire fighting appliance) is required in the surrounding area and water will be isolated if the water main requires maintenance or repair. Indirect system A cold water storage tank located on or within a roof space, or in a service room at the top of a high-rise building is supplied with water directly or indirectly (pumped) from the water main. The supply pipe is called a ‘rising main’. The size of the tank or tanks will be dependent on the number of occupants and the type of sanitary fixtures within the building. Some buildings will have separate storage tanks for cold supply, hot supply, flushing water and central heating make-up water. Water to all fixtures, excluding potable water outlets, is supplied from the storage tanks. The indirect system will ensure a constant flow of water is maintained throughout the building during peak draw-off times. Benefits of the indirect system include: The storage cistern provides a backup supply of water if the water main is isolated. The reduced pressure eases wear on valves and fittings. The reduced pressure minimises the possibility of noise and water hammer. The possibility of contaminating the potable supply is negated by the tank’s air gap. Break tanks In a high rise building with a large water demand, a large volume of water is needed to be stored if adequate pressure is to be maintained. Rather than designing a building with a roof that will support the weight of water required for the entire building, the building is divided into zones of about 30 metres head or 10 floors. Break pressure tanks are placed at the top of each zone and supply water to the floors within the zone. If break tanks are needed in a multi-storey building, then depending on the number of levels and the design of the system, the building will contain multiple break tanks on different levels. This will split the pressure into more manageable zones. Another option is to install a pump in the system. This is especially important if the pressure in a gravity-fed system will not be adequate without the use of a pump. Most high rise buildings have a plant room or rooms that accommodates a variety of services. If multiple break tanks are needed, then they will take up space on multiple floors. This may reduce the number of rooms or office space, but it will be better overall for the business. The water pressure will be better, and less power is needed to supply water. 30609.1  Page 25 of 31 Flushing storage tank (internal header tank) This storage tank may supply water to flushing cisterns, urinal flushing or to flushing valves. In a building containing several water closets (WC), a flushing valve can be installed at each WC which is supplied with water from the tank. When activated, the flushing valve releases a pre-set quantity of water to the pan, then automatically closes. The advantages are: no time delay between flushes no cistern overflow required no cistern filling noise neat and tidy installation may be easily concealed and vandal proof. Mains pressure models are also available. External elevated reservoir An external elevated reservoir is an outdoor water tank/reservoir that is raised off the ground. The elevated height is used to create water pressure (or head) without using a pump. Depending on why the reservoir is installed, the capacity and the height off the ground will change. Large installations can be used as town supplies, and small installations can be used by homeowners/residents. In the previous topic of hot water systems, low pressure hot water installations were covered, and external elevated reservoirs work on the same concept. Pressure is measured in kilopascals (kPa); in low pressure hot water installations, this is sometimes referred to as ‘metres head’ or head pressure. Head pressure or metres head is the term used for the fact that: As the height of a column of water increases the pressure at the base of the column also increases. Each metre in height increases the pressure at the base by 9.81 kPa, this is often rounded up to 10kPa for every metre to make calculating the pressure easier. The amount of water pressure exerted or available at any point of a system can be determined by measuring the height difference between the top of the water level in the system and the point in question. In a low pressure header (ceiling) tank system, the height of the ceiling tank determines the hot water pressure (metres head). The tank is usually installed as high as possible to provide the maximum amount of pressure achievable, without exceeding the pressure rating of the cylinder. Systems that are gravity fed and with the required height will provide the required water pressure, without the need for a pump. A pump may still be required for other parts of the system. 30609.1  Page 26 of 31 Town supplies External elevated reservoirs that are used to supply a town are also called water towers. These are often installed in areas of the city with the highest elevation. One example is the Invercargill Water Tower (pictured). This tower (built in 1889) is over 42 metres tall and housed a 300,000 litre steel tank that supplied pressurised water to the city. More modern water towers are usually much larger and taller. In the United States, towns can have multiple water towers to supply residents, where the water is drawn from ground tanks, pumped up to the tower, then gravity fed to the town. For example, one tower in Edmond, Oklahoma, is almost 50 metres tall and can hold over 1,892,700 litres (500,000 gallons). Invercargill Water Tower Swollib (c) 2006 CC BY-SA 3.0 (Wikimedia) Residential supplies In homes, a tank can be elevated to create more water pressure without the use of a pump to deliver water (gravity fed). These are often used for irrigation/outdoor uses, emergency supplies, and could also be used for drinking water if treated. For example, if you wanted a rainwater supply that could be used for irrigation/outdoor uses, then you could install an elevated tank or barrel as a reservoir. Councils and territorial authorities will have different rules on elevated water tanks, and installations may need a building consent. This is often dependant on the water tank capacity and how high above the ground you want to install the tank. AS/NZS 3500.1 Section 8 contains design and installation requirements for tanks. If you designed the system to AS/NZS 3500.1, then all requirements would apply. This includes a base, stand or support that is designed to ‘adequately support the weight’ of the tank when filled. A system that is used to supply the house, either for sanitary plumbing only or for all uses, would need a pump to operate. 30609.1  Page 27 of 31 Emergency water supply Water supply systems (water mains) may serve one or several buildings. Some Territorial Authorities (TAs) may require building owners to install and maintain independent water tanks or supply systems for emergencies. In other situations, such as rural housing, there may not be any option if there is no water main reticulation available. Most high rise buildings have a plant room at the top that accommodates a variety of services. Many modern buildings store massive quantities of water below ground level for the sole purpose of fighting fires or for other emergencies. Emergency water supplies can also be required based on what the building will be used for. G12/AS1 paragraph 5.1.1 requires buildings having the classification of community care (hospitals, old persons homes, prisons) to be provided with cold water storage of no less than 50 litres per person. Councils/TAs may give suggestions to households to prepare them for an emergency. The Wellington Region Emergency Management Office (WREMO) asks residents to be prepared for natural disasters/other emergencies where services such as power or water mains may be damaged. They provide information and resources for water storage and use during an emergency. For example, they partnered with a water tank manufacturer to make a 200 litre water tank and kit available for a reduced cost. Firefighting The Local Government Act 1974 requires a supply of firefighting water within urban New Zealand. For other parts of the country such as rural areas, an emergency water supply for firefighting may be needed. Some commercial and industrial buildings require a form of firefighting capability. Under the Building Act 2004, certain building consents must be supplied to the Fire Service Commission, and they make suggestions such as firefighting water supplies. 30609.1  Page 28 of 31 If a water fire suppression system is needed, a supply of water separate from the domestic supply may be necessary. It is important to ensure a correct volume and pressure of water is available if it is ever needed. AS/NZS 3500.1 section 6.4 states water requirements where water will be used as a reservoir in case of a fire. This also includes backflow prevention devices installed in the bypass piping. Section 8 goes into detail about water storage tank installation requirements. In addition to standards, work must also meet the requirements of the local council. Territorial Authorities will have their own laws for water supplies that must be followed in urban and rural areas. Activity 4 1. Which system is most suited to high-rise structures, a direct or indirect system? 2. How are break tanks divided between floors in a multi-storey building? 3. According to AS/NZS 3500.1 Section 8, what is the first general design and installation requirement for tanks? 4. G12/AS1 states requirements for buildings classed as community care. What is the estimated “daily use” in litres per person given for the following activities? A daily use of WC Washing Drinking 30609.1  Page 29 of 31 Activity answers Activity 1 1. What are the three waters managed by the territorial authority? Drinking water, stormwater, wastewater 2. Is rainwater used as a public supply, alternative supply, or both? Used as an alternative supply (self-contained) Activity 2 1. The customers are a family of 6 who live on a small lifestyle block right on the edge of the city. They currently use mains supply but are sick of paying high water bills. They are looking for a low maintenance system to reduce their water bill and supplement the mains supply water by supplying all of their sanitary plumbing needs. Their largest water use is the bath/shower, as they have two young children and two teenagers. Best system: rainwater system Reasons: One of the lower maintenance systems compared to bore water or grey water. With a good setup, regular maintenance should be quick and easy. Because their property is small and on the edge of the city, they may not have access to a bore for water. A grey water system is high maintenance. The household would need to watch their use of soaps and detergents, and clean out the filters regularly. Because they have younger children, they would also have to be careful with grey water as baths and showers may be contaminated with human waste. 30609.1  Page 30 of 31 2. A couple wants to build a new ‘eco’ house in a rural area about an hour from Christchurch. They would like to minimise their impact on the environment by getting their water from alternate sources. They are not scared of high maintenance or large set up costs. Their goal is to create a system that is as sustainable as possible. Solution could use any/all three water supplies. For example, because of the rural area, they may be able to get a permit for a bore. Rainwater is a common alternative solution that should be used. Grey water could also be used, as they are ok with higher maintenance solutions. Activity 3 1. G12 states that “buildings provided with water outlets, sanitary fixtures or sanitary appliances must have safe and adequate supplies.” Give one way of making sure that a house supply is safe, and one way of making sure it is adequate. Safe: treating water through filters, backflow protection, signs/labelling of potable and non-potable supplies, protecting the water source e.g. fences, regular testing of the supply Adequate: making sure that tank is large enough for its intended use, monitoring water levels, having a backup supply e.g. mains water or top-up that has an adequate flow rate for the demand Activity 4 1. Which system is most suited to high-rise structures, a direct or indirect system? Indirect system 2. How are break tanks divided between floors in a multi-storey building? The building is divided into zones of about 30 metres head or 10 floors 3. According to AS/NZS 3500.1 Section 8, what is the first general design and installation requirement for tanks? Materials used to construct tanks shall be as specified in Section 2 30609.1  Page 31 of 31 4. G12/AS1 states requirements for buildings classed as community care. What is the estimated “daily use” in litres per person given for the following activities? A daily use of WC 20 litres Washing 25 litres Drinking 5 litres As per G12/AS1 5.1.1 (grey comment box) 30609.1 earnlearn-tepukenga.ac.nz 0800 327 648 (0800 EARN IT)