Shop NorthStock for a large selection of seatless, full-port, double-disc and tri-flow check valves. Check valves provide the ultimate protection in preventing liquid or gas flow reversal in system pipelines. Tri-Flow check valves are spring loaded valves that can be adjusted from full flow to complete shut-off. With a graduated position indicator, Tri-flow check valves are easy to adjust and control flow and its automatic shut-off helps to prevent water-hammer. The Tri-flow is three products in one as it takes the place of a balance valve, shut-off valve, and check valve.