The term Water hammer describes the loud, banging noises in the pipes which are caused when the water which has built up momentum flowing through the pipes is suddenly stopped by a rapidly closing valve. When water hits a sudden wall, it does not compress it lashes back in a wave. This causes a severe spike in pressure. Because of these hydraulic pressure spikes, water hammer can loosen pipes and damage fittings.
Water hammer is the pressure caused when a fluid in motion is suddenly stopped or is made to change its direction. It is also known as hydraulic shock. A water hammer usually occurs when a valve closes at the end of a pipeline system. This pressure can cause a lot of serious problems, such as an explosion or collapse of the pipe, and appendages due to loud sound, and vibration.
Water hammer can be experienced in domestic plumbing in dishwashers, washing machines, and toilets. It can also happen in hydroelectric generating stations. It can be heard as a loud banging, repetitive banging, or as some shuddering.
The effect of water hammer can be significantly reduced with the help of water hammer arrestors. Water hammer arrestors are hydro-pneumatic devices similar in principle to a shock absorber. When installed between the water pipe and the machine, it absorbs the shock reduces pressure in the piping system to safe levels.
Dishwashers, clothes washers, fast closing positive shutoff valves incorporated in the system, all contribute to creating water shock which is not only annoying but damaging to pipes and appliances. Water Hammer Arrestors incorporate a permanent pre-charged sealed air chamber to absorb the shock. The sealed chamber prevents the loss of air to the water and ensures long and trouble-free life. All potential leak points are permanently sealed.
All building water supply systems in which quick acting valves are installed must be provided with devices to absorb the hammer caused by high pressures resulting from the quick closing of these valves. These pressure absorbing devices shall be approved mechanical devices and the water pressure absorbing devices shall be installed as close as possible to quick acting valves.