A sparge arm is a piece of brewing hardware used to flush the grain bed with hot water in order to extract any residual sugars left behind in the mash. The sparge arm water needs to be in the range of 168° F in order to liquefy the remaining sugars; if the temperature exceeds 170° F, the brewer many risk pulling excess tannins from the grain husks and causing off flavors and chill haze in the finished beer. Sparge arms are typically constructed of copper, stainless steel, or plastic, and should have some form of flow control so that the approximate flow rate can be set to keep pace with the flow of wort leaving the mash tun (or lauter tun) and heading to the boil kettle.
Below are three examples of home brewing sparge arms. From left to right, there is a MoreBeer.com “Ultimate Sparge Arm,” a rigid copper sparge arm, and a fly sparge arm with a stainless bracket. I have used each one of these and am currently using the MoreBeer.com sparge arm due to its versatility, which allows me to integrate it into my RIMS system.