Water hammer is a pressure surge or wave caused when a fluid, usually a liquid but sometimes also a gas, in motion is forced to stop or change direction suddenly; a momentum change.
Here’s why water hammer arresters are important to have at home, and also how they work to protect your plumbing system. Water hammer arrestors are used to absorb the shock when water flowing in a piping system suddenly stops due to fast closing shutoff valves, dishwashers, and clothes washers. Watch the video from Got2Learn for more info:
The sliding piston of the Water Hammer Arresters absorbs sudden pressure changes and keeps the pipes from banging, the working principle of this is that air is 25 times lighter than water and will be trapped in a vertical vessel that acts as a shock absorber.
Water in the pipe below the air pocket will push against the trapped compressed air, the higher the water pressure the smaller and more compressed the air pocket becomes and visa versa thus absorbing water shock waves.At home, a water hammer may occur when a dishwasher, washing machine or toilet shuts off water flow.