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. Water Tite 86592 Shock Buster™ 1/4 in. Compression Copper Water Hammer Arrestor is one trustworthy water hammer arrestor which goes for long years flawlessly. It absorbs pressure to keep pipes from banging; prevents costly damage. It is approved for sealed-wall installations; no access panel required.