PrintUnloader Valves Intended for clean water applications with roller or piston pumps, these higher pressure valves are used to relieve pressure. Specs/Part #s Approx. Wt. Ounces Outlet/Inlet (NPT) Number of Ports Max. Temp. Max GPM Adjustable GPI Model Number 8 3/8"M x 3/8"M 2 200ºF 5 300-600 HPP33900062D 400-1000 HPP33900063D 800-1500 HPP33900067D