Check Valves

check valve

Check Valves by John Valves

The check valve, also known as a non-return valve, is used in piping systems to restrict and stop backflow. The fluid that passes through a pipeline creates pressure and flow velocity that opens the valve and allows for unobstructed flow. On the flip side, the reversal of flow will cause the valve to close. Operation specifics can vary based on the valve’s mechanism.

Pumps, compressors and other pieces of equipment in the discharge line always have a check valve fitted to prevent backflow.

We locally manufacture and supply a wide range of check valves, including:

  • Bronze swing check valves
  • Vertical lift check valves
  • Cast and ductile iron swing check valves
  • Tilting disc check valves
  • Duo check valves
  • Ball check valves
  • Cast and forged steel globe valves
  • Cast steel swing check valves
  • Forged steel swing and piston check valves
  • Silent check valves
  • High-pressure check valves (up to 6200kpa)
Swing Check Valves

Our range of swing check valves include the John Fig 4B and 4BF bronze swing check valves which conform to Australian Standard AS1628. They have been designed for non-return duties in either horizontal or vertical pipelines, conveying water or other fluids not harmful to copper alloys.

These swing type valves have a disc that is unguided as it opens or closes completely. Swing check valves offer very low levels of turbulence and pressure drop. They are commonly found in applications within mechanical services, domestic water systems, fire protection and hospital equipment.

Lift Check Valves

Our range of lift check valves work automatically with line pressure in horizontal pipelines, but only with the bonnet vertically above the valve. They come with a flow arrow on the side of the valve body which indicates the correct direction for installation.

These types of valves are flow restricting and therefore are generally used as a companion to the globe valve.

Piston Check Valves

Our range of piston check valves includes the John 521 & 522. They feature a stainless steel disc and seat with precision lapped faces. This allows for easy inline refurbishment or replacement if necessary. The metal to metal locked up bonnet seal means pressure-tight sealing when in service. With a union nut bonnet connection, dismantling for maintenance purposes is simple.

Cast Iron Ball Check Valves

The function of our John 408 cast iron ball check valve is similar to the piston check valve. However, these ball check valves use a “ball” inside the body to control the movement of flow. The ball is free to rotate, resulting in even wear and a wiping action between the ball and seat. This feature makes ball checks useful for viscous media like sewerage.

These non-clog valves need minimum maintenance and provide trouble-free performance in both the horizontal and vertical position.

Frequently Asked Questions About Check Valves

Got questions? Below are some of the questions we get asked often about check valves.

Check valves are usually installed in pipelines to prevent backflow. A check valve is a valve which allows free flow one way, but not the other. For example, if the flow direction reverses, the valve will close. Where no check valve is present, reverse flow back through the pump or compressor can result in these expensive pieces of equipment rotating backwards resulting in significant damage.

The selection of the correct check valve for an application is critical. Selection of the wrong type of check valve could result in the occurrence of pressure surges (water hammer) which can be forceful enough to do significant damage to piping, pumps and other valves. Our engineers can help assist with the correct check valve selection for your specific application.