Description: Part # 100558 is a 1/2" thermal relief valve designed for hot water pressure washers up to 145°F. The valves help to protect the pump from damage due to heat build-up when the machine is in bypass mode. It does this by discharging a small amount of heated water upon sensing a rise in temperature, which then allows cooler water to enter and cool down the pump. An innovative cap design allows flow to be diverted according to operator preference, and the valve may be mounted in the pump manifold, inlet water supply, or bypass loop plumbing. Maximum PSI: 125. Maximum Temperature: 145°F. Inlet Size: 1/2" MNPT. Outlet Size: 1/4" Plastic Hose Barb.