WATER HAMMER

Water hammer is the destructive forces, pounding noises and vibration in a piping system when water  flowing through a pipeline is stopped abruptly.  When water hammer occurs, a high intensity pressure wave travels back through the piping system until it reaches a point of some relief.  The shock wave will then surge back and forth between the point of relief and the point of stoppage until the destructive energy is dissipated in the piping system.  The violent action accounts for “banging”, “thumping”, and/or intense vibration in the pipe line.  Although noise is generally associated with the occurrence of water hammer, it can occur without audible sound or noise.  Quick closure always causes some degree of shock with or without noise.  The common cause of water hammer  is single lever faucets (sinks/lavatories) or automatic solenoid valves (dishwashers, washing machines, etc.).  The speed of the valve closure time is directly related to the intensity of the surge pressure.

The only effective means of control is to install water hammer arrestors.  These devices have diaphragms which separate an air chamber from the water in the piping system.  As the shock wave reaches this device, the air chamber absorbs the shock.  Arrestors should be located as close as possible to the source of the shock wave.