Pipe requirements; concrete, CI, PPR pipes

Requirements of a good pipe material

1. Strength: withstands internal pressure, water hammer and external loads (soil, traffic).
2. Durability: long life, resistant to corrosion, chemical attack from soil and water, and to abrasion.
3. Smooth interior: high Hazen-Williams C value, low friction loss, and no growth of deposits.
4. Safe for water: no taste, colour, toxic or bacterial effect on the water carried.
5. Easy joints: watertight, flexible and quick to make.
6. Light and easy to handle and transport; available in many sizes and lengths.
7. Low cost, including laying and maintenance, and locally available.
8. Easy to repair, to tap for connections, and to extend later.

Concrete pipe

• Plain, reinforced (RCC) or prestressed pipes, made in sizes from about 150 mm up to 2–3 m; they are economical mainly in large diameters.
• Merits: cheap in large diameters, long life, does not corrode, can be cast locally, smooth interior.
• Demerits: heavy, difficult to transport and lay, may leak at joints, can be attacked by acids and sulphates, and cracks under tension and shock; used for large gravity mains and low-pressure lines (up to about 60 m head, more for prestressed).

Cast iron (CI) pipe

• Strong, durable (100 years), resists corrosion, stands high pressure and loads; the socket-spigot or flanged joints are easy.
• Heavy, costly, brittle; the interior roughens (tuberculation) so cement lining is provided.

Polypropylene random copolymer (PPR) pipe

• Light plastic pipe, joined by heat fusion to make a leak-free joint; resists corrosion and scaling; handles hot water up to 95 °C; non-toxic and long lived.
• Costly, needs fusion machine, expands on heating; not for large diameters.