Analysis and Testing of Freezing Phenomena in Plastic Piping Systems

Abstract

Failure of plastic piping due to freezing occasionally occurs in fire sprinkler systems and water supply lines. The cost of these pipe breaks can be significant, particularly for those that occur in high-rise buildings. The costs may include repair, loss of service, and water damage. In a previous paper, the theory and testing of the freezing failures in metal pipes was investigated, demonstrating that the pipe breaks are due to a pressure rise between the frozen section of the pipe and the blind end of the system. The pipe typically fails at a weak link in the system at a significantly elevated pressure, remote from the freeze area. This paper describes additional testing on plastic pipes, including PVC, CPVC, and PE, that are used in many water supply and sprinkler systems. In the previous study, a critical length of frozen pipe was calculated that would cause the burst due to overpressure remote from the freeze. In the case of plastic piping, the length of time that the pipe is over-pressured also affects the failure due to creep effects. Prior freeze failures in a plastic piping system may cause damage to the remaining non-failed pipe that could lead to future failures even if another freeze event does not occur.