Maintain pump prime and prevent backflow in fuel or water systems.Groco's Bronze Check Valves can be used vertically or horizontally in fuel or water systems to maintain pump prime or prevent backflow to the fluid source. Their unique design reduces flow turbulence and restriction, and improves pump performance. Cast bronze construction provides excellent resistance to harmful corrosion. These machined bronze valves feature female NPT threaded ports on each end.Bronze fittings have an outer surface that is rough in feel and appearance, almost like its covered with sand. Thats because bronze fittings are sand cast, and then machined.Threads are tapered "NPT," which stands for "National Pipe Thread."