Check Valves

A check valve, or non-return valve, allows flow in one direction and closes automatically to stop reverse flow. It is self-acting: forward flow opens the disc or ball and a fall in forward flow, aided by gravity, a spring or reverse pressure, closes it. Check valves protect pumps from reverse rotation, prevent backflow between pressure zones and keep suction lines primed. Choosing the right type matters, because a poorly matched valve can either slam and cause water hammer or fail to close reliably at low differential pressure.

The swing check valve is the general-purpose choice for water and wastewater. A hinged disc swings clear of the bore under forward flow and drops closed when flow stops, giving low head loss and simple maintenance. Dual-plate (wafer) check valves use two spring-loaded half-discs on a central hinge in a short, light body that fits between flanges, suiting building services and space-limited installations.

For lines where rapid flow reversal is likely, such as pump discharge, the nozzle or axial-flow check valve closes a spring-loaded disc over a very short travel before the flow reverses, largely eliminating slam and the resulting pressure surge. Lift and piston check valves guide the disc vertically off the seat and suit smaller-bore, higher-pressure process lines. Ball check valves are simple and tolerant of viscous or dirty media.

Governing standards include EN 12334 and EN 16767 for water and industrial check valves, API 6D and API 594 for pipeline and wafer designs, with flanges to EN 1092 or ASME B16.5 and testing to EN 12266 or API 598. Bodies are made in ductile iron, cast and stainless steel and bronze, with seat materials chosen for the medium. Orientation matters: confirm whether the line is horizontal or vertical and the direction of flow.

To specify a check valve, provide the bore, pressure rating, medium, installation orientation, expected flow range and any water-hammer concern. We can then recommend a type and materials suited to the closure behaviour the system needs.