XIM’s reversing check valve allows fluid flow in one direction only. However, when the need arises to drain the plumbing connected to the inlet end of the valve, it allows air to enter the side port without withdrawing fluid from the plumbing after the check valve. Passage control is accomplished with a silicone valve material that resists fluid buildup and remains functional even when the fluid contains small solid particles. We test each valve after assembly for leak-free function at 25 psi. Valves are functional in a temperature range of 35°F to 140°F.