Piping systems in any building construction are designed to serve the following primary purposes.
- To supply water everywhere in the building
- To dispose of rain water above ground
- To remove water from water cupboards and washbasins etc.
- Drainage of soil and waste water in septic tank or town sewer.
The major types of pipes available in the market for fulfilling the above purposes are as follows.
- cast iron pipe and fittings
- plastic or pvc pipe
- Galvanized Steel (GI) Pipe
- stoneware pipe
- Asbestos Cement (AC) Pipe
- concrete pipe
1. Cast Iron Pipes
Cast iron pipes and fittings are primarily used for the design of soil and rainwater disposal systems. These pipes are made by sand pouring process or spinning.
Sand cast pipe is made by pouring molten cast iron into vertically mounted sand molds. They are available in 1.5, 1.8 and 2 m lengths and 5 and 6 mm thicknesses.
Spun pipe is made by pouring molten gray cast iron into a revolving water-cooled mould, forming a seamless pipe up to 3 meters in length, which is less than sand cast pipe.
2. plastic or pvc pipe
There are 3 common types of plastic pipes available in the market, as given below.
- Unplasticized PVC (UPVC) or rigid pipe for use with cold water
- Plasticized PVC pipes that are plasticized with the addition of rubber. It has lower strength and lower working temperature than UPVC pipe.
- Chlorinated PVC (CPVC) pipe that is 120 . can withstand high temperatures of up to0 (used to carry hot water)
For pipes used in soil and wastewater discharge systems, the wall thickness shall be greater than the thickness used for roof drainage.
45. Rigid PVC pipe is used for the distribution of water at temperatures below0C.
At higher temperatures, the strength of the pipe decreases. Similarly, ultraviolet radiation from sunlight and frequent changes in temperature shortens the life of PVC pipe.
These pipes are costlier than AC pipes but cheaper than GI pipes.
3. Galvanized Steel (GI) Pipes
GI pipes are made from steel pipes. In the galvanizing process a thin layer of zinc is deposited which protects it from corrosion.
They are available in light, medium and heavy grades depending on the thickness of the metal. For 15 mm GI pipe, the thickness is 2.0, 2.65 and 3.25 for light, medium and heavy grades respectively. Generally medium range pipe is used for internal plumbing in the building.
These pipes corrode easily if it contains salt water or is hidden in lime concrete and brickwork or buried under the ground.
These pipes are costlier than PVC pipes.
4. stoneware pipes
These pipes are available as internal diameter 10mm to 600mm with thickness varying from 12mm to 43mm.
A good stoneware pipe should give a sharp clear tone when struck with a light hammer.
These pipes are extensively used as underground drainage pipes in low cost construction buildings. Generally these pipes are laid on a uniform bed of concrete and further specified for laying in different types of soil. However, experienced workers and a good supervisor are required to lay these pipes. Therefore, in many places, preference is being given to PVC pipes instead of these pipes.
These pipes are cheap.
5. Asbestos Cement (AC) Pipes
These pipes are also used for drainage and ventilation of rainwater from roofs, soil and waste. They come in two profiles – one with beading around the socket (WB) and the other without beading around the socket (WOB). The latter type is more common than the former.
Pipes come in lengths of 3 metres.
The main drawback of these pipes is that they are heavy and break easily.
These pipes are cheaper than PVC pipes.
6. concrete pipe
Unreinforced pipes of smaller diameter as well as reinforced and prestressed concrete pipes of larger diameter are available for water supply and other uses.
Small non-reinforced concrete pipes are heavily used to drain rainwater.
Large diameter pipes are generally used for major water supply works.