In any building construction piping systems are designed to serve the following primary purposes.
- To supply water everywhere in the building
- For the disposal of rain water above the ground
- To dispose water from water closets and washbasin etc
- To drain soil & waste water to septic tanks or town sewers.
The principal types of pipes that are available in the market to serve the above mentioned purposes are as follow.
- Cast iron pipes and fitting
- Plastic or PVC pipes
- Galvanized steel (GI) pipes
- Stoneware pipes
- Asbestos Cement (AC) pipes
- Concrete pipes
1. Cast Iron Pipes
Cast iron pipes and fitting are primarily used for designing of soil and rain water disposal systems. These pipes are made by the sand cast process or by spinning.
Sand cast pipes are made by pouring molten cast iron into vertically mounted sand moulds. They are available in 1.5, 1.8 & 2 metre length and 5 & 6 mm thickness.
Spun pipes are made by pouring molten grey cast iron into a revolving water cooled mould, producing a seamless pipe in length upto 3 metre with thickness less than sand cast pipes.
2. Plastic or PVC pipes
There are 3 common types of plastic pipes are available in market, as given below.
- Unplasticized PVC (UPVC) or rigid pipes for use with cold water
- Plasticized PVC pipes which are plasticized with addition of rubber. It has lower strength and lower working temperature than UPVC pipes.
- Chlorinated PVC (CPVC) pipes which can withstand higher temperatures upto 1200 (used to carry hot water)
For pipes used in soil and waste water discharge systems, the thickness of the wall will be larger than that of used for roof drainage.
Rigid PVC pipes are used for distribution of water with temperature below 450C.
At higher temperature, the strength of the pipes decreases. Similarly ultraviolet radiation from sunlight as well as frequent changes in temperature reduces the life of PVC pipes.
These pipes are costlier than AC pipes but cheaper than GI pipes.
3. Galvanized Steel (GI) Pipes
GI pipes are made from steel pipes. The galvanizing process deposits a thin coating of zinc which protects it from corrosion.
They are available in light, medium and heavy grades depending on the thickness of the metal. For a 15 mm GI pipe, the thicknesses are 2.0, 2.65 & 3.25 for the light, medium and heavy grades, respectively. Generally the medium grade pipes are used for internal plumbing in building.
These pipes corrode easily if it carries brackish water or concealed in lime concrete and brickwork or buried under the ground.
These pipes are costlier than PVC pipes.
4. Stoneware Pipes
These pipes are available in the form of internal diameters 10 mm to 600 mm with thickness varying from 12 mm to 43 mm.
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. Usually these pipes are laid on an even bed of concrete and further treated as specified for laying in different types of soils. However laying of these pipes requires experienced workmen and good supervisor. Therefore PVC pipes are being preferred to these pipes in many places.
These pipes are cheap.
5. Asbestos Cement (AC) Pipes
These pipes are used for drainage of rainwater from roofs, soil and waste and also for ventilation. They come in two profiles – one with beading around socket (WB) and the other without beading around socket (WOB). The latter type is more common than the former.
The pipes come in lengths of 3 meters.
The principal defects of these pipes are that they are heavy and they break easily.
These pipes are cheaper than PVC pipes.
6. Concrete Pipes
Unreinforced pipes of small diameters as well as reinforced and prestressed concrete pipes of large diameters are available for water supply and other uses.
Small unreinforced concrete pipes are very much used for drainage of rain water.
Large diameter pipes are generally used for major water supply works.