The 6" Watts 994RPDA Series Reduced Pressure Detector Assembly (RPDA) backflow preventer began production in 1991 and is still currently in production. The body is contructed of stainless steel and uses a single victaulic coupler cover. The 994RPDA utilizes plastic cam checks and a self contained stainless steel relief valve. The relief valve may be removed from the body by unthreading it, but use caution when doing so, as to not "squeeze" or warp the relief valve body. The cam checks thread into the body. Although not necessary, a cam check removal tool is available to remove the check assemblies for the 2 1/2 - 6" sizes. Bypass valves should be a 3/4" Watts 009-M3.