PRESSURE WASHER CHECK VALVE by PACheck valves allow water to flow through the pump in one direction, and help control chemical flow. They can also be used as back flow preventers, and as inline check valves. Check valves may be included at a number of points in the system. There is a check valve in the chemical line foot, as well as a pressure actuated unloader. Rated at: 6500 PSI 6. 5 GPM stainless steel Available in: 1 4" 3 8"