May 2007 Siphonic Drainage

We have received reports that problems have occurred with siphonic drainage. The problems reported are excessive shaking / vibrating of pipe work and pipes or outlets fracturing.

With buildings becoming ever larger, the pipe work runs for siphonic drainage by necessity become longer and longer.

From our research, we understand that the HDPE pipe will expand or contract by 0.18mm per linear metre per °C

Therefore, if we assume a pipe length of say 150m, with an internal roof level temperature of 30°C. When rainwater enters the building at say 2°C there is a tendency for the pipe to contract by 150 x 0.18 x 28 = 756mm .

This amount of contraction clearly has the potential of causing problems not only to the pipe work, but also the gutter joints

Our advice is to consider the use of such methods carefully, and check for any recent developments with regard to this relatively new problem.

< back>