Water Supply: Pipe Materials

• Pipes are a large proportion of the capital invested in water supply undertakings, so pipe materials are selected based on durability, life, and overall cost, including installation and maintenance.

Metallic Pipes

• It includes Cast iron, Ductile iron, Steel, and Galvanised Iron
• Unlined metallic pipes are discontinued.
• Metallic pipes are lined with cement mortar or epoxy lining

Non-metallic Pipes

• It includes Reinforced Concrete, Prestressed Concrete, Bar Wrapped Steel, Cylinder Concrete, and Asbestos Cement
• Plastic pipes include PVC (PVC-O, PVC-U), Polyethylene, and Glass Reinforced Plastic

Cast Iron Pipes

• Diameters range from 80 mm to 1050 mm, supplied in 3.66 m and 5.5 m lengths, and covered with protective coatings.
• A variety of joints available including socket, spigot, and flanged joints
• Classified as LA, A, and B according to thickness and Class LA pipes have been the evolving basis for the series of pipes.
• Well-suited for pressure mains and laterals where tapings occur for house connections.
• Advantages: Good lasting qualities, strength, durability, corrosion resistance with coating, and suitability for pressure mains and laterals.
• Disadvantages: Heavy weight, high transport costs, short length, high jointing costs, low tensile strength, liability to inner surface defects, and potential breakage during transportation/jointing.

Ductile Iron Pipes

• Made with magnesium added to molten iron of low sulphur content via a metallurgical process.
• Provided with cement mortar lining at the factory via centrifugal process for consistent thickness throughout its length.
• Diameters range from 80 mm to 1000 mm, in lengths of 5.5 to 6 m.
• Advantages: High resistance against breakage due to impact, high tensile strength comparable to mild steel, good for higher working pressure, traditional corrosion resistance like cast iron, lighter than cast iron.
• Disadvantages: Heavy weight, transportation and jointing difficulties, poor adaptability in laying/jointing, and poor response to surge pressures

Galvanised Iron Pipes

• Manufactured using mild steel strips of Low Carbon
• Available in tubes of 6 mm nominal bore to 150 mm nominal bore.
• Different classes of tubes are available like Light (Yellow), Medium (Blue) and Heavy (Red) depending on wall thickness.
• Generally used for distribution of treated or raw water in rural or hilly regions due to its light weight and easy jointing.
• Not recommended for house service connections due to its high corrosivity.
• Advantages: Higher durability, longevity, weld consistency and integrity, amenable to fabrication, superior finish with anti-rust coating, greater corrosion resistance, superior bend ability and ease of cutting and threading.
• Disadvantages: Should not be used underground unless properly covered, may hide defects beneath zinc coating, can contain lead that corrodes quickly, and may have rough inner patches causing failures/stoppages that are expensive to repair.

Steel Pipes

• Manufactured with steel produced by open hearth or electric furnace, or through basic oxygen processes.
• Pipes can be manufactured as seamless, electric resistance welded, or submerged arc welded pipes.
• Smaller diameter pipes can be made from solid bar sections via hot or cold drawing processes and are referred to as seamless.
• Advantages: Highly elastic, strong, easy to install, high flow capacity, leak resistance, long service life, reliable, versatile, economical and cost-effective.
• Disadvantages: Corrosion is the biggest material consideration, Welding joints are complicated and require skilled labour, susceptible to internal tuberculation and external corrosion and electrolysis if not protected, anti-corrosion increases price, and need for air vacuum valves to prevent collapse increases costs further.

Asbestos Cement Pipes

• Made of asbestos paste and cement mixture compressed by steel rollers to form a laminated material of great strength and density.
• Manufactured from classes 5 to 25 with nominal diameters of 80 mm to 600 mm with the test pressure of 5 to 25 Kg/cm².
• Advantages: Smooth inside surface, flexible joints, anti-corrosive, cheap, and light in weight.
• Disadvantages: Not resistant to impact damage, cannot be located with standard line location equipment, difficult to locate with specialized location equipment, does not transmit sound vibrations well, and contains potential health concerns and risks during repair/replacement.

Reinforced Cement Concrete Pipes

• Classified as P1, P2 and P3, with test pressures of 2.0, 4.0, and 6.0 Kg/cm2.
• Working pressure should not exceed 2/3 of the test pressure for gravity mains, or 1/2 for pumping mains.
• Advantages: Good corrosion resistance, widespread availability, high strength, and good supporting load capacity.
• Disadvantages: Requires careful installation to avoid cracking, heavy, susceptible to attack from aggressive soils, and poor adaptability in installation.

Prestressed Concrete Pipes

• Suited for water supply mains with pressures in the range of 6 kg/cm2 to 20 kg/cm2.
• Two types in use: lined cylinder and non-cylinder.
• Cylinder lined pipe is available in inside diameters from 16 to 48 in. and embedded cylinder pipe has been manufactured larger than 250 in. in diameter; Lengths are generally 16 - 24 ft.
• Non-cylinder type consists of a concrete core pre-compressed in longitudinal and circumferential directions by a highly stressed wire.
• Advantages: Good corrosion resistance, widespread availability, high strength, and good load supporting capacity.
• Disadvantages: Requires careful installation to avoid cracking, heavy, susceptible to attack from aggressive soils, and poor adaptability in installation.

Bar Wrapped Steel Cylinder Concrete Pressure Pipes

• Available in diameters of 250 mm to 1600 mm, with higher diameter pipes designed for working pressures up to 25 kgs/cm2.
• Pipes have an effective length of 4 m to 8 m and longer length pipes can be custom made.
• Advantages: Semi-rigid or semi-metallic properties; resistant to impact, stiffer than conventional steel pipes, less expensive bedding cost, corrugated surface increases structural stability, cheaper and low maintenance.
• Disadvantages: Heavier than pipes like DI, HDPE, DWC, PVC, GRP pipes making them difficult to handle and rough handling may damage the outer coat or inner lining

Plastic Pipes

• Includes PVC (polyvinyl chloride) pipes.
• UPVC (unplasticized polyvinyl chloride) pipes.
• OPVC (oriented polyvinyl chloride) pipes.
• CPVC (chlorinated polyvinyl chloride) pipes.
• Polyethylene (PE) pipes.
• HDPE (high density polyethylene) pipes.
• MDPE (medium density polyethylene) pipes.
• GRP (glass fibre reinforced plastic) pipes.

PVC Pipes (polyvinyl chloride)

• Rigid PVC pipes weigh only 1/5th of conventional steel pipes of comparable sizes.
• Pipes are available in outer diameters from 20 to 315mm at working pressures of 2, 5, 4, 6, 10 Kg/cm2.
• Advantages: Resistance to corrosion, light weight, toughness, rigidity, economical in laying, jointing and maintenance, and ease of fabrication
• Disadvantages: Deteriorating effect by direct sunlight, water hammer causes stretching, and non-conductive material

UPVC Pipe (unplasticized polyvinyl chloride

• A plastic pipe made of polyvinyl chloride (PVC) resin without any plasticizer
• Used for supplying drinking water; often made of polyethylene (PE) or polyvinyl chloride (PVC), and are used for transportation of water
• Advantages: Lightweight, easy to install, economical, good corrosion resistance, smooth surface reduces friction losses, long pipe sections reduce leakage/ infiltration potential, flexible
• Disadvantages: Susceptible to chemical attack especially solvents, strength affected by sunlight, not suitable for above ground installations, requires great care during laying, and susceptible to damages due to external pressure and blows in above ground level application

OPVC Pipe (oriented polyvinyl chloride)

• By stretching the material under certain conditions of pressure, temperature, and speed, it is possible to orient the PVC polymer molecules in the same direction, resulting in a layered structure called Oriented Poly Vinyl Chloride Pipes of highest Orientation Class 500 with homogeneous Socket including supply of Elastomeric sealing ring.

• Manufactured for different sizes in India: 110mm, 160mm, 200mm, 250mm, 315mm and 400mm with pressure ratings of PN 12.5, PN 16 and PN 25.

• For conveyance of cold water under pressure, which is suitable for conveyance of water, including potable water, up to and including 45°C, where special performance requirements are needed, such as impact loads and pressure fluctuations, up to pressure of 2.5 MPa.

• Advantages: Greater lightness and easy handle, excellent flexibility, greater hydraulic capacity, higher chemical resistance, higher hydrostatic resistance, and higher resistance against water hammers.

• Disadvantages: Susceptible to chemical attack especially solvents, strength affected by sunlight, and not suitable for above ground installations.

CPVC Pipe (chlorinated polyvinyl chloride)

• The chlorinated polyvinyl chloride polymer from which the pipe compound is to be manufactured must have a chlorine content > 66.5%.
• Chlorinated polyvinyl chloride pipe compounds, containing additives like modifiers, lubricants, and fillers, must have a density between 1450 kg/m3 and 1650 kg/m3.
• Nominal size of CPVC pipe varies from 15 mm to 150 mm.
• The wall of the plain pipe must not transmit more than 0.1 percent of the visible light falling on it when tested in accordance with IS 12235 (Part 3): 2004, Reaffirmed 2019.
• Advantages: Lightweight and easy for transportation, requires fewer tools for installation and maintenance, lack of plasticizers discourages microbial growth, corrosion and abrasion resistance, reground into pellets and recycled, and reduces heat loss due to lower thermal conductivity.
• Disadvantages: High thermal expansion coefficient and slightly costlier than other PVC pipes.

HDPE (High Density Polyethylene) Pipes

• A type of flexible plastic pipe used for water supply systems
• Made from high density polyethylene, suitable for high pressure pipelines.
• Advantages: Lightweight, easy to install, economical, good corrosion resistance, smooth surface reduces friction losses, long pipe sections reduce leakage/infiltration potential, flexible.
• Disadvantages: Susceptible to chemical attack especially solvents, strength affected by sunlight, and not suitable for above ground installations.

MDPE (Medium Density Polyethylene) Pipes

• Used for consumer connection pipes as an alternative to GI pipes.
• Available in sizes ranging from 20 mm to 110 mm dia for pressure class of PN3.2, PN4, PN6, PN10 and PN16.
• Applications: Water distribution for town, rural & irrigation projects, cold water plumbing reticulation, household water connections from the main supply, and compressed air lines.
• Advantages: Very smooth inner surface ensures no scaling and choking; has less friction loss, gives better flow at lower heads, easy to transport and store as the pipes available in 100, 200 and 300 metre coils, no wastage of pipe as it can be cut, fewer joints thanks to flexibility and easy repair, easy tapping with specialty tapping joints, plus tools-off installation is possible with precision made fittings.
• Disadvantages: Susceptible to chemical attack with certain solvents and strength may be affected by sunlight.

GRP (Glass Fibre Reinforced Plastic) Pipes

• Five pressure classes of pipes, PN 3, PN 6, PN 9, PN 12 and PN 15, correspond to the working pressure ratings of 3.06, 6.12, 9.18, 12.24 and 15.30 kg/sq.m, respectively.
• Stiffness is the prime design criteria for underground pipes.
• Classified into four classes, A, B, C, D, depending on the type of installation, overburden above the crown of the pipe and the soil conditions.
• Widely used in other countries requiring corrosion resistant pipes at reasonable costs.
• Advantages: High strength to weight ratio, corrosion resistant, lightweight compared to metallic and concrete pipes, longer length and minimum joints for faster installation.
• Disadvantages: High material cost, brittle, require careful installation, high installation cost.

Pipe Joints

• Pipelines are often long and pipe networks are also huge
• Pipes are available in finite lengths
• Pipes need to be jointed to develop long pipelines and networks
• The basic requirement of pipe joints are: a) Water tightness b) Strong enough c) Durability d) Economy e) Workability
• There are various types of pipe joints

Bell and Spigot (Socket and Spigot Joints)

• This creates a recessed "bell" end which receives the plain "spigot" end of the adjoining pipe

Lead-caulked joints (bell and spigot)

• Very popular in earlier days, but they are discontinued because of concerns of toxicity caused by lead in the drinking water.

Mechanical joints (bell and spigot)

• Used when cast iron pipes are joined.
• Special metallic collar is fitted in the spigot portion around the cast lug and tightened against the bell portion using nut and bolt.
• Gaskets are often used to make it water tight.

Flanged Joints

• Most common-type pipe joint used in steel piping systems.
• For cast iron pipe systems, pipes come with flanges at both ends.
• For mild steel or carbon steel pipes, the flanges are either screwed down or welded at the ends.
• A rubber or leather gasket is often used to make the joints water tight
• Rigid joints which cannot be used where deflections or vibrations may be expected.

Dresser Coupling

• It is also a type of mechanical joint.
• Used when two pipes with plain end need to be joined
• A special type of mechanical collar is fitted and tightened over the ends.
• A gasket and an iron ring are slipped over each of the abutting ends of the pipes and a iron sleeve is inserted between the gaskets as a pipe stop.
• The iron rings are tightened by means of bolts.
• Strong and rigid joints that can withstand vibrations

Victaulic Coupling

• Special type of coupling to join pipes of materials and across multiple fire protection, industrial and commercial applications.
• Proprietary joints, and can be made rigid, and flexible to suit the application.

Valves

• Installed throughout water systems, to control water magnitude and direction
• All valves have a movable part that extends into the pipeline for opening or closing the internal pipe area.
• Four basic valve types are: slide, rotary, globe and swing; other types are sphere, diaphragm, sleeve and vertical-lift disk
• Valves generally operate by screw, gear or water pressure.
• Screw stems are in Gate, Globe, and needle valves.
• They can be manually operated hand-wheel or by a motorized operator/actuator.
• Large valves in high pressure system gear-operated .
• Can be operated by manual, electric, hydraulic or pneumatic actuators.
• Geared operation is common in butterfly, gate, globe and ball valves.
• Swing check, pressure relief valves are example of water pressure operated valves.

Gate valves

• Most abundantly used valve in water systems
• Mainly used for sectionalizing the pipe networks so that any maintenance area can be isolated with minimum service disruption.
• In pumping stations/treatment plants, shutoff valves (gate valve) install in inlet, outlet/ bypass lines to facilitate maintenance and repair
• Indian Standard Codes are IS 778, IS 14846 and IS 13114

Butterfly Valves

• Dual Purposes: Shut-off (ON-OFF), and regulate or control flow.
• Indian Standard Code is IS 13095 (Butterfly valves for general purposes).

Ball Valves

• Indian Standard Code is IS 9890: Ball valves for general purpose

T-PORT 90 TURN

• It shows its positions and how it turns

Non-Return Valve or Check valves

• Indian Standard Codes are IS 778, IS 5312
• Types: Lift Check, Swing Check and Flap Check.

Air Valves

• Air entrapped inside a piping system can cause severe damage inside the pipeline.
• Increased are head loss, decreased capacity, enhanced corrosion, reduced pump efficiency, valve malfunctioning and unwanted vibrations.
• Air movement is necessary when pipes are being filled or emptied,
• Air valves release air to allow pipes to be filled or emptied
• Air valves releases entrained air accumulated at high points.
• Air valves acts as vacuum breaker saving pipes from implosion.
• Without air valve, it is also not possible to drain a pipe completely.

Globe Valve

• Indian Standard Codes are IS 778, IS 13114 and IS 10605
• Circular seal is axially connected to a vertical spindle and hand wheel where seating is a ring perpendicular to the pipe
• Flow changes direction through 90 degrees twice, resulting in high head loss within the valve.
• Suited in small bore pipelines and are used for flow control through pipes.
• A house tap on the wash basin is a Globe valve

Scour Valves

• Located at low points or valved sections of pipelines.
• Allows periodic line flushing to remove sediment.
• Allows line drainage for maintenance/repair
• Located at the lowest point and connected to natural drainage channels.
• Must not located below a stream/drain, as it can avoid backflow of contaminated water into drinking water.
• The size should depend on water volume to drain.