The use of plastics for non-pressure sewer pipes is of comparatively recent origin and is still in the experimental stages.
However, some countries, such as the Netherlands, Scandinavia, France, etc., have already begun to use plastic pipes for sewers of 250 mm dia and above on a moderate to large scale (15% to 25% or so).
Their use is hardly 5-7 per cent in Germany and the United Kingdom, and almost no plastic pipes are used in India for laying sewers, although, they are increasing the use of plastic pipes for internal water supply and drainage fittings.
In addition, plastic pipes of up to 1.50 mm dia have also begun to be used in house connections of India to carry sewage to the municipal sewers.
Although, the use of plastic pipes for non-pressure sewers is not very promising, however, advanced plastic technology has increased the use of plastic sewers.
The test results on uPVC pipes have shown that:
- These pipes continue deformed for about two years; the deformation rate decreases over time.
- Its deformation is mainly influenced by the type and method of application of the backfill material.
- Traffic loading has a little effect on the final deformations, but it reduces the time to achieve equilibrium conditions; and
- Due to excessive deformation, a PVC pipe failed to operate as part of an operational sewer system.
The most advanced development of a rib-reinforced solid wall uPVC pipe (ULTRA- RIB), which has been largely tested in U.K and Scandinavia, has shown very much satisfying results.