Swing Check Valves

Swing check valves use a hinged disc that swings open under forward flow and drops shut the instant flow reverses. They give the lowest pressure drop of any check design on water and larger-diameter lines, which is why they are the default backflow protection for pump discharge, municipal water, HVAC, and irrigation mains. Apex Flow Solutions stocks swing check valves from 1/2 in. threaded brass up through large-diameter ductile iron flanged bodies, sold by the single unit.

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How a swing check valve works

Forward pressure lifts the disc off its seat; when flow stops, the disc falls closed under its own weight and any reverse pressure. There is no spring, so the valve adds very little restriction, but it also relies on gravity, which is why orientation matters. On lines where flow stops abruptly and slam is a concern, a spring-loaded design closes faster. Compare the two on our check valve selection guide, or browse spring check valves if you need instant closure.

Materials and sizes we stock

Threaded brass swing checks from 1/2 in. to 4 in. for water, air, and oil service. 316 stainless swing checks for chlorine, acids, and corrosive process lines. Ductile iron flanged swing checks built to AWWA C508 for municipal and waterworks duty, including UL/FM listed models plus lever-and-weight and spring-assist options for surge control on the 9620 series. Solder-end brass models are available for copper systems.

Installation and orientation

Install a swing check horizontally, or vertically only when flow runs upward, so gravity helps the disc seat. Mount it with the flow arrow pointing downstream and the bonnet on top for horizontal runs. Installed backwards, or in downward-vertical flow, the disc will not seat correctly. See the orientation guide for diagrams.

Common questions

Swing check or spring check?

Choose a swing check for low restriction on water and larger lines where flow changes gradually. Choose a spring check where flow stops suddenly and you need to prevent water hammer, or where the valve must sit in a vertical downflow line.

Can a swing check valve mount vertically?

Only on vertical-upflow lines. On downward flow the disc cannot fall onto its seat, so use a spring or inline check instead.