November 21, 2017

PP vs. PVC for pipes and fittings for sewer, drainage applications

 A lack of knowledge in South Africa about the use of polypropylene (PP) for sewer and drainage pipes and fittings for underground gravity sewers and drains may lead to the premature failure of sewer lines if incorrect products are specified.

While PVC sewer fittings are all rated 400 KPa (SN 8), both SANS 8773 and SANS 21138 allow lower stiffness ratings for fittings. A lower stiffness rating makes for a thinner wall thickness and therefore a cheaper product. Low-stiffness pipes and fittings are intended for use in shallow drains, whereas SN 8 (400 kPa) pipes and fittings can be used in all drains and deep sewers.

“The South African market is not well educated to look for, and know, the difference. Hence SN 2 (100 kPa) and SN 4 (200 kPa) PP sewer fittings are sometimes installed in main sewer lines, an application they were not designed or intended for. This may lead to premature failure of sewer lines,” DPI Plastics Technical and Product Manager Renier Snyman warns.

“PP is a new entrant, while having a minimal track record in the sewerage and drainage market, compared to PVC, both locally and abroad,” Snyman points out. His call for increased awareness about PP versus PVC comes in the light of PP fittings for sewer and drainage applications slowly being introduced into the local market.

DPI Plastics offers a full product range of PVC pipes up to 630 mm and fittings are available for these sizes. However, only 110 mm PP sewer fittings are available in South Africa. “This means that a full system and size range of pipes and fittings are not available locally in PP material,” Snyman cautions.

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