Plumbing: Cold Water Systems PDF

CHAPTER 5 COLD WATER SYSTEMS INTRODUCTION The supply of fresh, wholesome cold water to people’s homes is a basic human need. As a plumber, it is your job to get the water from the main external stop valve to the taps so that it is clean and f...

CHAPTER 5 COLD WATER SYSTEMS INTRODUCTION The supply of fresh, wholesome cold water to people’s homes is a basic human need. As a plumber, it is your job to get the water from the main external stop valve to the taps so that it is clean and fit for human consumption. Most people take for granted the supply of cold fresh water to their homes and few would probably appreciate the degree of work necessary to provide this service. In this chapter, we will look at the subject of water from the cloud to the tap, the cleaning process that makes it fit for human consumption, the distribution of water and the systems that you will install. We will also explore the regulations that govern our industry and the processes you will need to understand to enable you to work safely and correctly on domestic cold water systems, from installation planning to testing, maintenance and fault finding. By the end of this chapter, you will have knowledge and understanding of the following: the sources and properties of water the types of water supply to dwellings the treatment and distribution of water the sources of information relating to cold water systems the water service pipework to dwellings how to select cold water systems the system layout features of cold water systems fed from private water supplies the components used in boosted (pumped) cold water supply systems from private sources for single-occupancy dwellings backflow protection the Water Regulations how to install cold water systems and components how to carry out commissioning procedures how to replace or repair defective components how to decommission cold water systems. 1 SOURCES AND There is no new water on Earth – all water is about 4.2 billion years old, whether it is sea water (saline), PROPERTIES OF river or stream water, groundwater, fossilised water or water from the polar ice caps. WATER The rainwater cycle Water is a simple compound made up of two hydrogen O atoms attached to a single atom of oxygen, with the chemical symbol H2O. Water is tasteless and odourless and, in small quantities, it is colourless, while in large H H quantities it possesses a light blue hue. p Figure 5.1 Water molecule 201 9781398361614_Ch05.indd 201 21/04/22 10:27 AM  The City & Guilds Textbook: Plumbing Book 1 Water moves constantly in what is scientifically may remain on the surface, where it will eventually find called the hydrological cycle. We know it by its more its way into rivers, streams, lakes or the oceans. Here, common name: the rainwater cycle. the process begins again, an example of the Earth’s natural recycling process. Simply explained, the rainwater cycle is a natural process where water is continually exchanged between the atmosphere, surface water, groundwater, soil water Sources of water and plants. It can be divided into three main transfer If we look at all of the water on Earth, 97 per cent is processes: saline (sea) water and only 3 per cent is fresh water. Of 1 evaporation from oceans and other water bodies fresh water, nearly 69 per cent (or 2.07 per cent of the into the air Earth’s total water resources) is trapped in the polar ice 2 transpiration from land plants and animals into the caps and glaciers, and 30.7 per cent (0.9 per cent of the air total water resources) is groundwater. It is groundwater 3 precipitation from water vapour condensing from that the population of the Earth relies on for its drinking the air and falling back to Earth or into the ocean. water supply. Su at Fr ate Ri % es r rf er w % ve w 3% ac h 2 rs e 0. 3 Sw am Gr ou 11 ps % Water saturated cloud wa nd 30 ter.7% Water vapour Sal sea ine o Lak Rain and snow w r e Heat from the Sun 97 ater Ice 87 s % ca % an ps gla d Evaporation ci 69 ers % p Figure 5.3 Distribution of the Earth’s water River running back to the sea to restart the process The total freshwater supply for the world is in the region p Figure 5.2 The rainwater cycle of 1350 trillion litres, the majority of which is stored on the ground, where it is available in reservoirs, streams, As the Sun warms the Earth, water on its surface rivers, lakes, etc., with a further 13,650 trillion litres evaporates. This vapour rises with the air and is carried in the form of water vapour, which will eventually fall by the prevailing winds. If the vapour passes over land, as rain. Conversely, about 1100 trillion litres of water some of it condenses to form clouds and, as more evaporates into the atmosphere worldwide every day. water vapour is attracted or the ground rises (hills or mountains), the cloud becomes saturated to the point Sources of water in the UK where it can no longer hold the moisture and the vapour Of the rain that falls on the UK annually, only 5 per cent is released in the form of rain, sleet, snow or hail. is collected and stored in reservoirs for the drinking water On reaching the ground, there are many paths it may supply. The rest flows in rivers to the sea or is filtered follow. Some of it may be re-evaporated back into the down to the natural water table or aquifers that exist atmosphere; it may be absorbed by the ground, where below the ground surface. The main sources of water in it will travel towards the water table or aquifer; or it the UK are shown in Table 5.1. 202 9781398361614.indb 202 20/04/22 1:42 PM  Chapter 5 Cold water systems  Table 5.1 Sources of water in the UK Source of water Description Properties of water from this source Deep wells Machine-dug wells that draw their water from below the Usually good-quality water, as extracted from shallow impermeable strata (see Figure 5.4). below the Earth’s surface. Shallow wells Wells dug by hand or excavator that penetrate only the first Must be considered dangerous because it can water-bearing strata, or aquifer, in the Earth’s surface (see be contaminated with water from cesspits or Figure 5.4). broken drains, etc. Upland surface Water that has collected in upland lakes and rivers without The main water source for the north-west of water passing through the Earth’s strata. England. It is not contaminated with salts and minerals, and is naturally soft and acidic. Spring A naturally occurring flow of water from the Earth’s surface. The purity of the water is highly dependent on the distance it has travelled from the source. River A large natural flow of water, usually starting as a small Usually poor quality due to industrial pollution. stream on high ground, which enlarges with distance The cost of treatment is high. travelled. Usually terminates at the sea and can be tidal, such as the River Avon. Canals Most canals are a product of the Industrial Revolution and Very poor quality, generally used only for for many years fell into dereliction. Many, though, have been industrial purposes and irrigation. cleaned and re-opened, and are now sites of natural beauty. Aquifers Naturally occurring water-bearing strata, often deep beneath Very high quality, but prone to contamination the Earth’s surface. Mostly consist of permeable rock, such by nitrates from farming. as sandstone, gravel silt or clay, which soaks up water like a sponge (see Figure 5.4). Artesian wells Water that rises from underground water-bearing rock layers Usually very good quality as the water is and springs under its own pressure, but only if the well head is below the filtered naturally through layers of rock. level of the water table (see Figure 5.5). Boreholes Man-made wells that are drilled directly to a below- Very high-quality water that, in most cases, is groundwater source and the water extracted for use if cleaner than the water undertaker’s water main. connection to a water main is extremely difficult. Filtering and chlorination are not necessary, although the quality should be monitored. Lake Deep well Land spring Unconfined aquifer Shallow well Impervious strata INDUSTRY TIP Pervious strata Confined aquifer The Environment Agency is the overseeing authority for all Impervious strata watercourses in the UK. It samples p Figure 5.4 Deep and shallow wells about 7000 river and canal sites 12 times a year to test their Artesian spring Artesian well Impervious strata chemistry and nutrients so it can see Plane of saturation whether there are any pollutants and whether it needs to target areas for improvement. Impervious strata Water-bearing strata p Figure 5.5 Artesian wells and springs 203 9781398361614.indb 203 20/04/22 1:42 PM  The City & Guilds Textbook: Plumbing Book 1 These changes are aesthetic only and do not constitute INDUSTRY TIP a health risk. Typical situations where this may occur in domestic properties are: The information in this section on fluid categories is water heated in a hot water secondary system taken from the Water Supply (Water Fittings) Regulations mixed fluid categories 1 and 2 water discharged 1999 document, accessible at: www.legislation.gov.uk/ uksi/1999/1148/contents/made from combination taps or showers water that has been softened by a domestic common salt regeneration process. The UK fluid categories Fluid category 3 Fluid category means a category of fluid as described Fluid category 3 is water that constitutes a slight health in Schedule 1 of the Water Supply (Water Fittings) hazard because of the concentration of low-toxicity Regulations and/or Scottish Water Byelaws. Any water substances. Fluids in this category are not suitable for that is not cold wholesome drinking water supplied by drinking or any other domestic purpose or application. a water undertaker can be classed as a potential hazard. The substances might include: The Water Supply (Water Fittings) Regulations 1999 list ethylene glycol (anti-freeze), copper sulphate or five fluid categories, as described below. similar chemical additives such as heating inhibitors, Fluid category 1 cleansers and descalers sodium hypochlorite and other common Fluid category 1 is wholesome water supplied by a water undertaker, complying with the Water Quality disinfectants used in domestic properties. Regulations made under Section 67 of the Water Typical fluid category 3 situations occur in the Industry Act 1991. It must be clean, cold and potable. following. All water undertakers have a duty to supply water In houses, apartments and other domestic that conforms to these regulations, which ensure dwellings: wholesome water suitable for domestic use or food water in the primary circuits of heating systems, production purposes. Whenever practicable, water whether chemicals have been administered or for drinking water purposes should be supplied direct not from the water undertaker’s mains without any water in washbasins, baths and shower trays intervening storage. clothes-washing and dishwashing machines home dialysis machines KEY TERM hand-held garden hoses with a flow-controlled Potable: drinkable, from the Latin word ‘potabilis’ spray or shut-off valve meaning drinkable. hand-held fertilisers. In premises other than single-occupancy domestic dwellings: INDUSTRY TIP domestic fittings and appliances such as washbasins, baths or showers installed in The three words commonly used to describe fluid category 1 commercial, industrial or other premises may be are wholesome water, potable water and drinking water. regarded as fluid category 3; however, if there is a potential for a higher risk, such as a hospital, Fluid category 2 medical centre or other similar establishment, Fluid category 2 is water that would normally be then a higher fluid category risk should be classified as fluid category 1 but whose aesthetic applied in accordance with the regulations quality has been impaired because of: house-garden or commercial irrigation systems a change in temperature without insecticides. a change in appearance, taste or odour owing to the presence of substances or organisms. 204 9781398361614.indb 204 20/04/22 1:42 PM  Chapter 5 Cold water systems Fluid category 4 hose union bib taps in a non-domestic installation Fluid category 4 is water that constitutes a significant sinks, WC pans, urinals and bidets health hazard because of the concentration of toxic permeable pipes in any non-domestic garden, substances, which can include: whether laid at or below ground level chemical, carcinogenic substances or pesticides grey-water recycling systems. (including insecticides and herbicides) Medical: environmental organisms of potential health laboratories significance. any medical or dental equipment with Typical fluid category 4 situations are as follows. submerged inlets General: bedpan washers and slop hoppers primary circuits of heating systems in properties mortuary and embalming equipment other than a single-occupancy dwelling hospital dialysis machines (commercial systems) commercial clothes-washing equipment in care fire sprinkler systems using anti-freeze chemicals homes and similar premises house gardens baths, washbasins, kitchen sinks and other mini irrigation systems without fertilisers or appliances that are in insecticides, including pop-up sprinkler systems non-domestic installations. and permeable hoses. Food processing: Food processing: butchery and meat trade establishments food preparation slaughterhouse equipment dairies vegetable washing. bottle-washing plants. Catering: Catering: dishwashing machines in healthcare premises commercial dishwashers and similar establishments refrigerating equipment. vegetable washing. Industrial and commercial installations: Industrial/commercial: dyeing equipment industrial and chemical plants industrial disinfection equipment laboratories photographic and printing applications any mobile tanker- or gulley-cleaning vehicles. car-washing and degreasing plant Sewage treatment works and sewer cleaning: brewery and distilling processes drain-cleaning plant water treatment plant or softeners that use water storage for agricultural applications methods other than salt water storage for fire-fighting systems. pressurised fire-fighting systems. Commercial agricultural: commercial irrigation outlets below or at ground Fluid category 5 level, and/or permeable pipes, with or without Fluid category 5 represents a serious health risk chemical additives because of the concentration of pathogenic organisms, insecticide or fertiliser applications radioactive material or very toxic substances. These commercial hydroponic systems. include water that contains: The list of examples of applications outlined above for faecal material or any other human waste each fluid category is not exhaustive. butchery or any other animal waste pathogens from any source. The distinction between fluid category 4 and fluid category 5 is often difficult to interpret. In general, Typical fluid category 5 situations are as follows. we can assume that fluid category 4 is such that General: the risk to health, because of the level of toxicity or industrial cisterns and tanks the concentration of substances, is such that harm 205 9781398361614.indb 205 20/04/22 1:42 PM  The City & Guilds Textbook: Plumbing Book 1 will occur over a prolonged period of days to weeks the obligations of the water companies and licensed to months, whereas the risk from fluid category 5, water suppliers to supply water that is fit for human because of the high concentration of substances or consumption, and the enforcement of those obligations the level of toxicity, is such that serious harm could by the Department for Environment, Food & Rural occur after a very short exposure of minutes to hours Affairs (Defra) and the Drinking Water Inspectorate to days, or even a single exposure. charging powers of water companies and suppliers, and the control of those charges by Ofwat KEY POINT protection of customers and consumers by Ofwat We must remember that fluid category 1 is clean, and the Consumer Council for Water. cold, wholesome water direct from the water Under the provisions laid down by the Water Act 2003, undertaker’s main and no other fluid category the UK Government introduced two documents that must come into contact with it or contamination regulate how plumbers install, commission and maintain may occur. water supplies within domestic buildings. These are: 1 the Water Supply (Water Fittings) Regulations 1999 2 the Private Water Supplies Regulations 2016. 2 THE TYPES OF WATER These will be discussed later in the chapter. SUPPLY TO DWELLINGS Sources of recycled, unwholesome water supply in domestic dwellings Types of water supply in Over the past 20 years, demand for water has the UK increased dramatically in the UK. Each of us now uses There are two types of water supply in the UK: an average of 150 litres of water every day for washing, 1 water supplied by a water authority, known as a flushing the WC, drinking, cooking, gardening and water undertaker, under Section 67 of the Water Act other household tasks. With the climate changing and 2 water supplied from a private source, such as a frequent periods of drought becoming a possibility, the borehole, river or stream. need to save water is becoming more apparent. There are many ways in which water usage can be The Water Act 2003 (Water Industry reduced in a dwelling, from simple rainwater collection Act 1991) in water butts for garden use, to more complex systems for clothes washing and WC flushing. We will look at INDUSTRY TIP these here. It must be remembered that this type of water is not fit for human consumption and must be Access the Water Act 2003 at: www.legislation.gov.uk/ marked as such. Any installation in a dwelling must not ukpga/2003/37/contents cross-connect with the mains cold water supply. The Water Act 2003 amalgamates and amends two There are three types of unwholesome water: previous pieces of legislation: the Water Industry Act 1 grey water 1991 and the Water Resources Act 1991. The Water 2 rainwater harvesting Act 2003 introduced changes to the regulation of the 3 black water. water industry in England and Wales originally made Grey water under the Water Industry Act 1991. It is enforced by the Environment Agency and deals with such matters as: Waste water from baths, showers, washing machines, the appointment and regulation of water and dishwashers and sinks is often referred to as grey water. sewerage companies and licensed water suppliers by About a third of all water used in the average the Water Services Regulation Authority (Ofwat) household is used for WC flushing. The water used water supply and sewage disposal powers, and for bathing from baths, showers and washbasins duties of the water companies and suppliers can be collected, cleaned and reused for this purpose. 206 9781398361614.indb 206 20/04/22 1:42 PM  Chapter 5 Cold water systems High-level grey water storage cistern Grey water supply Grey water feed Grey water collection to cistern in the roof space Grey water filter Underground storage cistern Submersible pump p Figure 5.6 Indirect grey water system feeding a WC Grey water is usually clean enough for use in WCs resources because water that would otherwise be lost with only minimal disinfection or micro-biological can be used to flush toilets, water gardens and feed treatment. Problems can arise when the warm grey washing machines, instead of using water direct from water deteriorates when stored, as the bacteria it the mains supply for such purposes. contains rapidly multiply, making the water smell. Rainwater harvesters can be installed at domestic or This can be overcome by filtration and treatment with commercial sites, and average households can expect chemicals. There must also be a means of protecting to save up to 50 per cent of their water consumption the mains water against contamination by backflow by installing a rainwater harvesting system. from a grey water system, in order to comply with the Water Supply (Water Fittings) Regulations 1999. Harvesters are usually installed beneath the ground in an underground storage cistern or on the roof of a Rainwater harvesting flat-roofed building. A typical four-bedroom house will Rainwater harvesting has the potential to save a capture enough water to keep a 5000-litre cistern in large volume of mains water and reduce pressure on use throughout most of the year. 207 9781398361614.indb 207 20/04/22 1:42 PM  The City & Guilds Textbook: Plumbing Book 1 High-level grey water storage cistern Grey water supply Rainwater is collected from the roof by the guttering system where it flows down the rainwater pipe, through a rainwater filter and into an underground storage cistern Grey water feed to cistern in the roof space Grey water filter Underground storage cistern Submersible pump p Figure 5.7 Indirect rainwater harvesting system Black water Unwholesome water will be revisited in Chapter 9, Black water is water and effluent from WCs and kitchen Sanitation systems. sinks that can be treated only by a water undertaker at a sewage works. 3 THE WATER TREATMENT PROCESS AND DISTRIBUTION OF WATER In this section, we will look at the way the water we use every day for drinking, washing and cooking is filtered, Sedimentation, filtration, cleaned and sterilised to ensure that it is fit for human sterilisation and aeration of consumption. The word we use to describe fresh, clean water water is ‘wholesome’. Before it is considered wholesome, the water undergoes several stages of treatment to ensure its cleanliness and 208 9781398361614.indb 208 20/04/22 1:42 PM  Chapter 5 Cold water systems quality. These stages are the responsibility of the water Sludge blanket level Inlet valve undertaker and are known as: Settled water channel sedimentation sterilisation Decanting trough filtration aeration. Sedimentation Sludge Slow sand filter Rapid sand filter concentrator cone Sterilisation Automatic sludge bleed valve Distribution Inlet pipe Bottom sludge extractor pipe p Figure 5.8 The water treatment process p Figure 5.9 Sedimentation tank Sedimentation Sedimentation tanks are designed to slow down the Filtration water velocity to allow the solids that the water Filtration is an important process that removes turbidity contains to sink to the bottom and settle under and algae from the raw, untreated water. There are gravity. Simple sedimentation may also be used to many different types of filter, including screens, gravel reduce turbidity. filters, slow sand filters, rapid sand filters and pressure filters. We will concentrate on three of these: KEY TERM 1 slow sand filters Turbidity: the cloudiness or haziness of water 2 rapid sand filters caused by particles that are usually invisible to the 3 pressure filters. naked eye. Turbidity is a key test of water quality. The difference between these types is not just a matter of the speed of the filtration process, but the Sedimentation tanks are usually rectangular in underlying principle of the method. Slow sand filtration shape, with a length to width ratio of 2:1, and are is a biological process and rapid sand filtration is a usually 1.5–2 m deep. The inlet and outlet must be physical treatment process. on opposite sides of the tank, and the inlet designed to distribute the incoming flow as evenly across the Slow sand filters tank as possible. The outlet should be designed to These are often preceded by micro-straining or coarse collect the cleared water across the entire width filtration. These filters are used primarily to remove of the tank. The tank will also require covering to micro-organisms, algae and turbidity. It is a slow but prevent external contamination. very reliable method of water treatment, often suited Sedimentation tanks require cleaning when their to small supplies, provided that there is sufficient area performance begins to deteriorate; a 12-monthly period to properly construct the filtration tanks. between cleaning operations is normally sufficient. 209 9781398361614.indb 209 20/04/22 1:42 PM  The City & Guilds Textbook: Plumbing Book 1 Slow sand filters consist of tanks containing sand KEY TERM with a size range of 0.15 mm to 0.30 mm, and to a depth of around 0.5 m to 1.5 m. For single dwellings, Floc: a collection of loosely bound particles or materials. These are bound together by the circular modular units, usually used in tandem, are coagulation process for easy removal from the available. These have a diameter of around 1.25 m. water. As the raw water flows downwards through the sand, micro-organisms and turbidity are removed by a simple filtration process in the top few centimetres Rapid sand filters are usually constructed from of sand. Eventually, a biological layer of sludge rectangular tanks containing coarse silica sand with develops, which is extremely effective at removing a size range of 0.5 mm to 1 mm laid to a depth of micro-organisms in the water. This layer of sludge between 0.6 m and 1 m. As the water flows downwards is known as the ‘schmutzdecke’. The treated water through the filter, the solids remain in the upper part is then collected in underdrains and pipework at the of the sand bed where they become concentrated. The bottom of the tank. The schmutzdecke will require treated water collects at the bottom of the filter and removing at periods of between 2 and 10 weeks flows through nozzles in the floor. The accumulated as the filtration process slows. The use of tandem solids are removed either manually every 24 hours filters means that one filter can remain in service or automatically when the head loss reaches a while the other is cleaned and time allowed for the predetermined level. This is achieved by backwashing. schmutzdecke to re-establish. A variety of proprietary units are available containing Slow sand filters should be sized to deliver between filtering media of different types and sizes. In some 0.1 m3 and 0.3 m3 of water for every 1 m2 of filter filters, the water flows upwards, improving the efficiency. per hour. Bellmouth Inlet Float-operated valve Filter media Inlet Backwash waste Schmutzdecke Fine sand Filtered water Gravel Outlet Wash water and air supply Perforated support Gravel tiles or underdrains p Figure 5.11 Rapid gravity filter  Figure 5.10 Slow sand filter Pressure filters KEY TERM These are sometimes used where it is important Schmutzdecke: ‘schmutzdecke’ comes from the to maintain a head of pressure to remove the need German word meaning ‘dirt cover’. to pump the water into the supply. The filter bed is enclosed in a cylindrical pressure vessel. Some small pressure filters are capable of delivering as much as Rapid (gravity) sand filters 15 m3/h. The cylinder is typically made of specially Rapid sand filters are predominantly used to remove coated steel, and smaller units can be manufactured the floc from coagulated water, but they can also be from glass-reinforced plastic. They operate in a similar used to successfully remove algae, iron, manganese and way to the rapid sand filter. water turbidity from raw water. 210 9781398361614.indb 210 20/04/22 1:42 PM  Chapter 5 Cold water systems Air release valve Inlet Sand Air and Washout wash water Gravel inlet Outlet Drain p Figure 5.12 Pressure filter Sterilisation Finally, water is treated with chlorine and ammonia Distribution of cold water before being allowed to enter the water supply. This There are two methods of water supply distribution will kill off any bacteria missed by the water filters. used in the UK. These are: Fluoride is still added in some parts of the UK, but only 1 gravity distribution in minute quantities. Ultraviolet (UV) water treatment 2 pumped distribution. uses a simple concept where water passes through a clear chamber where it is exposed to UV light. This UV KEY POINT light destroys the majority of bacteria and viruses that There are more than 2000 reservoirs used are present in the water. for drinking water in the UK. These are the responsibility of the Environment Agency. Control Diluting water inlet panel Gravity distribution The water from the collection of upland surface water is C impounded in reservoirs on high ground. Here, the water h Diluting water l is filtered by slow sand filters, and chlorinated before absorption tower o being fed to homes and factories by gravity. No pumping r is required. i n e Slow sand Service Chlorinating Water filter reservoir house main Reservoir Water main with injector p Figure 5.13 Sterilisation by injection of chlorine Aeration Aeration is commonly used to treat groundwater by mixing water with air. This removes dissolved metals p Figure 5.14 Gravity water distribution and gases like CO2 through chemical reactions and physical mixing. 211 9781398361614.indb 211 20/04/22 1:42 PM  The City & Guilds Textbook: Plumbing Book 1 Pumped distribution Service reservoir When water is taken from a river, it is pumped on a water tower direct to a settlement tank where all of the heavier impurities sink to the bottom. It is then passed through Pumping and chlorinating house a slow sand filter to remove any organic matter and Pump house Water chlorinated to wholesome water standard before being Settlement Slow sand main pumped to a water tower. From the tower, it flows via tank filter gravity to the water main. River p Figure 5.15 Pumped water distribution 4 SOURCES OF INFORMATION RELATING TO COLD WATER SYSTEMS The sources of information to be used when KEY POINT undertaking work on cold water systems are: BS EN 806 – Specification for installations inside statutory regulations buildings conveying water for human consumption industry standards is a relatively new British Standard that came into manufacturers’ instructions. force in 2011. It is divided into five parts: 1 General recommendations 2 Design Statutory regulations 3 Pipe sizing 4 Installation The Water Supply (Water Fittings) 5 Operation and maintenance. Regulations 1999 Linked with this is a second British Standard, BS Before 1999, each water authority had its own set of EN 8558 – Guide to the design, installation, testing water bye-laws that were based upon the 101 Model and maintenance of services supplying water for Water Bye-laws issued by the UK Government in 1986. domestic use within buildings and their curtilages. Together, these two publications replace the old The problem was that each water undertaker had local British Standard, BS 6700 – Design, installation, variations, which caused much confusion as there was testing and maintenance of services supplying no ‘common’ standard throughout the UK. water for domestic use within buildings and their curtilages. However, parts of BS 6700 that are On 1 July 1999, the Office of the Deputy Prime not covered in either BS EN 806 or BS EN 8558 Minister issued the first ever water regulations to be are retained. For further information contact The enforced in the UK. They are known as the Water Water Regulations Advisory Scheme. Supply (Water Fittings) Regulations 1999 and offer a common practice throughout the UK. They are linked Simply put, the Water Supply (Water Fittings) to a British Standard, BS EN 806 – Specification for Regulations were made under Section 74 of the Water installations inside buildings conveying water for Industry Act 1991 and have been put in place to ensure human consumption. that the plumbing systems we install and maintain prevent the following: 212 9781398361614.indb 212 20/04/22 1:42 PM  Chapter 5 Cold water systems contamination of water The Private Water Supplies Regulations 2016 stipulate wastage of water that a risk assessment must be made of all private misuse of water water supplies including the source, storage tanks, undue consumption of water any treatment systems and the premises using the erroneous metering of water. water supply. KEY TERM INDUSTRY TIP Erroneous: wrong; incorrect. A free copy of the Private Water Supplies Regulations 2016 can be downloaded here: www.legislation.gov.uk/ An important factor here is that these Regulations uksi/2016/618/contents/made cover only those installations where the water is supplied from a water undertaker’s water main, and are enforced by the water undertaker in your area. They are Industry standards not, however, enforceable where the water is supplied from a private water source. The British Standards (BS EN 806 – 1 A free copy of the Water Supply (Water Fittings) to 5 and BS 8558) Regulations 1999 can be downloaded from the The main British Standard for design, installation, relevant government pages at: www.legislation.gov.uk/ commissioning, testing, flushing and disinfection uksi/1999/1148/contents/made of systems is BS EN 806:2010 Specifications for installations inside buildings conveying water for The Private Water Supplies human consumption (in conjunction with guidance Regulations 2016 document BS 8558:2011 Guide to the design, A private water supply is defined as any water supply installation, testing and maintenance of services that is not provided by a water undertaker. It is not supplying water for domestic use within buildings connected to any part of the water mains network and their curtilages). and, as such, water rates are not charged, although In reality, the information has changed very little from the owner of any such supply may make a charge for the previous British Standard, BS 6700: 2006+A1: any water used. Private supplies are commonly used 2009 Design, installation, testing and maintenance in rural areas where connection to water mains is of services supplying water for domestic use within difficult. A private supply may serve one property or buildings and their curtilages, and this document many properties on a private network. The water may should be referenced where alternative information is be supplied from a borehole, spring, well, river, stream not available. or pond. The Building Regulations Under the Water Act 2003, the local authority in The Building Regulations make reference to cold water the area where the private water supply is located is services and systems. These are mentioned briefly responsible for the inspection and testing of the water in Approved Document G1 – Cold Water Supply supply to ensure that it is maintained to a quality that and Approved Document G2 – Water Efficiency. is fit for human consumption. These inspections and Additional recommendations can be found in Annex 1 tests are made in accordance with the Private Water – Wholesome Water and Annex 2 – Competent Person Supplies Regulations 2016. Generally speaking, the Self-certification Schemes. more people that use the supply, the more detailed the tests and the more regular the inspections Manufacturers’ instructions have to be. Supplies for commercial properties and Where appliances and equipment are installed activities, or food production and preparation, have to on a system, the manufacturer’s instructions are be tested more frequently and meet more stringent a key document when undertaking testing and requirements than domestic supplies. 213 9781398361614.indb 213 20/04/22 1:42 PM  The City & Guilds Textbook: Plumbing Book 1 commissioning procedures, and it is important that Trunk mains will vary in diameter depending on the these are used correctly at both installation and purpose of the main and the likely demand for the commissioning operations. Only the manufacturers supply. Pipes that transfer water to the various points will know the correct procedures that should be used in the distribution system can vary in diameter from to safely put the equipment into operation so that it 75 mm to 2.3 m. The size of the water main depends performs to its maximum specification. Remember: upon the size of the community that it serves. always read the instructions before operations  Table 5.2 The size of water main required depends on the size begin of the community it is to serve always follow the procedures in the correct order always hand the instructions over to the customer Town population Size of main (metres diameter) upon completion 500,000 1.05 m to 1.20 m failure to follow the instructions may invalidate the 200,000 0.75 m manufacturer’s warranty. 5000–20,000 0.2 m to 0.3 m When a new house has to be connected to the water 5 THE WATER SERVICE supply, the supply pipes are usually 25 mm in diameter. PIPEWORK TO At the boundary to the dwelling, a ‘screw-down stop valve’ is installed, so that the supply to the house can be DWELLINGS isolated if necessary while any repairs are carried out. Methods of connection to the Distribution of water in water main cities, towns and villages Underneath the road is the water main. The connection Water is supplied to our homes via a grid system for the water supply to the dwelling is made by a network of pipes known as trunk mains, a phrase brass ferrule, which is the responsibility of the water dating back to when the mains were constructed from undertaker. The ferrule is a type of shut-off valve that hollowed-out tree trunks. allows the water supply connection to be isolated for maintenance and repair. Water treatment The connection to the water main can be made in a plant number of ways depending upon the material from which the water main is made. For instance, if the water main is made from cast iron, then a self-drilling and tapping machine is used. With this tool, the water main is drilled, threaded and a ferrule inserted while the main is still under pressure so that the supply to other properties is not disrupted. If the main is made from PVCu or cementitious lined asbestos, then a brass strap-type ferrule is used. Water mains Houses and other buildings p Figure 5.16 Water supply grid system p Figure 5.17 A strap-type ferrule water main connection 214 9781398361614.indb 214 20/04/22 1:42 PM  Chapter 5 Cold water systems The supply pipe runs from the main external stop valve to the dwelling and is the responsibility of the house owner. It must be installed at a minimum depth of 750 mm and a maximum depth of 1350 mm. It must terminate within the building with a screw down-type stop valve with a drain-off valve installed immediately above the stop valve. Together, the communication pipe and the supply pipe make up the service pipe to the building. p Figure 5.18 A standard gunmetal ferrule KEY POINT From the water main to the building Figure 5.19 identifies a lot of important factors: pipe names, pipe depth and three points of The water supply from the water main into the building isolation. comprises two separate pipes: 1 the communication pipe, owned and maintained by The water supply to buildings can be arranged in the water undertaker numerous ways. In each case, separate dwellings 2 the supply pipe, owned and maintained by the supplied must have a controlling stop valve in a position owner of the building. that will allow the water supply to be turned off in an The communication pipe is installed by the water emergency without affecting any other property. undertaker from the ferrule on the water main to the Most water supplies in modern dwellings and industrial main external stop valve (also known as the boundary premises are piped in medium-density polyethylene stop valve because it is usually located at the boundary pipe (MDPE), which is coloured blue for easy of the property). It incorporates a gooseneck bend to identification to show mains cold (potable) water. This allow for any settlement of the roadway or pavement. is generally known as ‘blue poly’. The minimum pipe It is the sole responsibility of the water undertaker to size for modern dwellings is 25 mm. Soft copper to BS install, repair and maintain the communication pipe and EN 1057 R220 can also be used (in older properties main external stop valve. the cold mains may even be 15 mm copper). Household stop valve Communication Service pipe owned pipe owned and and maintained by the maintained by the building owner water undertaker 750 mm minimum 1350 mm maximum Ferrule Building water supply and 75 mm service duct Boundary stop tap isolator Boundary stop tap and water meter sealed at both ends chamber with No other service or Water cable in duct main hinged cover p Figure 5.19 The entry of the water supply into the building 215 9781398361614.indb 215 20/04/22 1:42 PM  The City & Guilds Textbook: Plumbing Book 1 Boundary stop valve 1 The usual and preferred method of supply, one stop valve to one house 2 This method is used where the communication pipe is long Joint communication pipe 3 This method is used where the communication pipe is long 4 This method is used where the supply pipe is long 5 This method is used where the Joint supply pipe is long supply pipe Water suppliers will normally insist on individual supplies to properties and DO NOT favour joint supplies (commonly called communal supplies). p Figure 5.20 Alternative methods of supplying more than one dwelling With new installations, a water meter is either fitted Water meters inside the dwelling are usually fitted to at the boundary to the property or in an external existing water supplies. They must be fitted between Groundbreaker-type meter box. This is so the customer two stop taps with a drain-off valve fitted after the does not have to be present when the meter is being meter but before the upper stop tap. read and to prevent illegal tampering with the water meter. Stop valve Drain off valve Meter Permanent cross bonding Stop valve p Figure 5.21 Groundbreaker-type meter box p Figure 5.22 Installation of an internal water meter 216 9781398361614.indb 216 20/04/22 1:42 PM  Chapter 5 Cold water systems There are many different stop valve/tap styles available, KEY POINT but they must comply with the Water Regulations and From the external main stop valve is where the BS EN 806. This, however, would not be acceptable plumber’s involvement with the Water Supply (Water Fittings) Regulations 1999 begins. From here on, when used as the lower stop tap on an internal water everything that we do to the cold and hot water meter installation as it would be possible to draw water system in the building is regulated to ensure that from the main before the water meter, leading to the water supplied is fit for its intended purpose. erroneous metering. Any stop tap used above or below ground must be Entering the property made from either gunmetal or corrosion-resistant brass, to prevent de-zincification of the stop tap. The When the water supply enters the property, it should Water Regulations state: terminate with a screw-down stop tap/valve complying Every water fitting shall be immune to or with the Water Regulations and BS EN 806. The Defra protected from corrosion by galvanic action or guidance to the Water Supply (Water Fittings) by any other process which is likely to result in Regulations 1999 is very specific: contamination or waste of water. As far as is reasonably practicable: Source: Schedule 2, Reg. 3 1 A stop valve should be located inside the building; and, All fittings that are made of a copper alloy, such as 2 Be located above floor level; and, brass or gunmetal, should carry either ‘CR’ or ‘GM’ markings on the fitting body to show that they are 3 As near as possible to the point where the corrosion resistant. supply enters the building; and, 4 Be so installed that its closure will prevent the A drain-off valve conforming to BS EN 1254 should be supply of water to any point in the premises. installed immediately above any stop tap/valve to allow Source: Section 4, G10.5 draining of the system. The diagram in Figure 5.23 illustrates the point. 6 SELECTING COLD WATER SYSTEMS So far, we have looked at how water is collected, 150 mm cleaned and distributed to houses and industry. We will now move on to look at the cold water systems we install in dwellings, their components, testing and maintenance. Each dwelling should have a wholesome (often called 75 mm service duct sealed at both ends ‘potable’, meaning ‘drinkable’) water supply, the most No other service or cable in duct important place being at the kitchen sink. In most domestic premises, it is likely that people will drink water from most of the taps. This means that water p Figure 5.23 The entry of the water supply to a property to all taps should be connected to the mains supply or The water authorities recommend that no more than come from a protected storage cistern. 150 mm of blue MDPE pipe be exposed above the floor Drinking water should also be provided in convenient level of the building. This is to minimise the amount locations in offices and other buildings, especially of MDPE pipework visible because MDPE decomposes where food is being eaten or prepared. under persistent exposure to the ultraviolet (UV) light present in daylight. 217 9781398361614.indb 217 20/04/22 1:42 PM  The City & Guilds Textbook: Plumbing Book 1 Domestic systems of cold l if a hot water storage vessel is to be installed, then a minimum of a 22 mm cold feed pipe is required, water supply increasing in size to reflect increased demand There are two basic systems of cold water used in to the hot water storage vessel supplied from a domestic dwellings: 100–150-litre cold water feed cistern in the roof 1 the direct system of cold water space 2 the indirect system of cold water. l on larger installations, a 22 mm rising main may be required, but this will depend on the water needs of The direct system of cold water the household. supply If a combination boiler or instantaneous water heater With this system, all cold water taps are fed direct from is installed, then a 15 mm mains cold water supply the mains supply. This means that all taps are provided should, in most cases, be sufficient, depending upon the with a supply of drinking water. Storage is required only supply pressure and flow rate. for supplying cold water to the hot water cylinder via a 150-litre cistern. A feed cistern will not be necessary if the hot water is supplied via an instantaneous hot 100–150 litre storage cistern fitted with water heater or ‘combi’ boiler. BS 1212 part 2 float-operated valve Spherical ball-type The direct system is the most commonly installed type service valve of cold water system in domestic properties because its installation is cost effective and there is usually a relatively high-pressure supply available.  Table 5.3 Advantages and disadvantages of the direct system of cold water supply 22 mm or 28 mm cold feed WC cistern fitted with Advantages Disadvantages to secondary hot water cylinder either a BS 1212 part 2 part 3 or part 4 float- Cheaper to install At times of peak demand, the 22 mm or 28 mm full-way operated valve pressure may drop gate valve or lever-type Drinking water at all fittings spherical ball valve Spherical ball-type Less pipework If the mains are under repair, the service valve property has no water Less structural support required in roof space for If there is a leak in the premises, the cold feed cistern there will be a great deal of damage due to high pressure More suitable for instantaneous showers, Can be noisy 15 mm mains cold water to all appliances hose taps and mixer fittings. Greater risk of contamination to Used in conjunction with a mains high-pressure (unvented) Drain-off valves Greater wear on taps and valves hot water supply More problems with water Smaller pipe sizes may be hammer used in most cases Greater risk of condensation Good pressure at all cold build-up on the pipework, which water outlets can easily be mistaken for a leak Pipe sizes for the direct system Pipe size depends on the system design but, generally speaking: l a 15 mm rising main will be large enough to supply p Figure 5.24 The direct system of cold water supply most cold water demands for a three- to four- bedroom house with all cold water outlets being supplied in 15 mm, including the bath 218 9781398361614.indb 218 20/04/22 1:42 PM  Chapter 5 Cold water systems The cistern should be installed as high as possible to increase the system pressure. 230–250 litre storage cistern fitted with BS 1212 part 2 float-operated valve Spherical ball-type service valve No water pipes or cisterns in the roof space. No risk of burst pipes due to freezing WC cistern fitted with either a BS 1212 part 2, part 3 or part 4 float-operated valve Spherical 22 mm or 28 mm cold WC cistern fitted with ball-type feed to secondary either a BS 1212 part 2, service valve hot water cylinder part 3 or part 4 float- operated valve 22 mm or 28 mm full way gate valve or lever- Spherical type spherical ball valve ball-type service valve 15 mm mains cold water to all appliances Appliance off the cold water mains 22 mm cold distribution pipework to the bath reducing to 15 mm to feed the wash hand basin and WC cistern Drain-off valves Drain- off valves p Figure 5.25 Direct cold water system with combi boiler or instantaneous hot water heater The indirect system of cold water p Figure 5.26 The indirect system of cold water supply supply Pipe sizes for the indirect system With this system of cold water supply, only the kitchen sink and the cold water storage cistern are fed directly Pipe size depends on the system design but, generally from the mains cold water supply. The other appliances speaking: l a 15 mm rising cold water main will be large enough are fed indirectly via the cold water storage cistern in the roof space. A large amount of water will, therefore, need to supply most cold water demands for a three- to to be stored to supply both cold water and hot water to four-bedroom house l the kitchen sink should be supplied with water direct appliances and fittings from a minimum of 230 litres of water stored in the cistern. The system is designed to be from the cold water main and 15 mm pipework is used in low-pressure water areas where the mains supply adequate for this; the cold water storage cistern can pipework is not capable of supplying the full requirement also be sup