In late 2019, BPDA carried out a number of high-pressure water jetting tests for a wide range of gravity pipe brands available in the UK market, including both concrete and lightweight plastic pipes. In this blog, we explore how significant are the findings from these tests and what do the results tell us about both concrete pipes and their lightweight alternatives.
In November 2019, BPDA carried out a number of jetting resistance tests on eight pipe samples using a 280 BAR pressure stationary water jet (equivalent to 4,000 psi). The two concrete pipe samples we tested both passed successfully. However, all lightweight pipe samples, made of different types of plastic, failed the testing criteria. Most of the failed pipe samples experienced internal layer piercing within 3 to 5 seconds only.
The test results come as no surprise. Four of the lightweight flexible pipes tested are manufactured to plastic pipe specification WIS 0-35-01 with a maximum water jet pressure requirement of 180 bar (2,600 psi) only. It is the same water jetting pressure limit specified in the Manual of Drain & Sewer Cleaning for plastic pipes (see Table). The problem was mainly associated with the time it took such pipes to fail:
Every year, Water Companies deal with 300,000 sewer blockages across Britain. High-pressure water jetting is the usual method used by cleaning contractors to deal with sewer blockages. Cleaning contractors can sometimes exceed 2,600 psi to deal with such blockages. However, the general advice currently is that cleaning contractors should not leave the water jet in one position for more than 60 seconds. It is unclear if such advice was offered with knowledge that some plastic pipes can experience damage after only 3 to 5 seconds of high-pressure jetting! The speed in which some of these samples were fully penetrated should make cleaning contractors and asset owners significantly worried.
After introduction of the new sewers’ adoption code, known as the Design & Construction Guidance (DCG), water companies can no longer introduce additional restrictions and requirements on lightweight pipes such as resistance to 4,000 psi water jetting. This may mean that the only way to protect our sewerage network is by the introduction of new higher limits for pipes’ jetting resistance. Even if a lightweight pipe cannot withstand high-pressure jetting for the entire testing period (which is 3 minutes), it should at least be resilient enough to withstand 60 or 90 seconds under such level of water jetting pressure.