Check valves, also known as non-return valves (NRVs), are an essential part of any industrial or residential plumbing system. They are used to prevent backflow, ensure proper system operation and prevent damage.

Check valves work fairly simply. The pressure created by the liquid flowing through the piping system opens the valve, and any reverse flow closes the valve. It allows fluid to flow completely unimpeded in one direction and automatically shuts off when pressure is reduced. While this is simple, there are different types of check valves with different operations and applications. How do you know which type of check valve to use in your job or project? To help you make the right choice, here are some details on the most common types of check valves.

Swing check valve
The White PVC Swing CheckSwing Check Valve utilizes a disc inside the valve to allow or stop flow in the piping system. When the fluid flows in the correct direction, the pressure forces the disc to open and keep it open. As the pressure decreases, the valve disc closes, preventing reverse flow of fluid. Swing check valves are available in a variety of material types, including PVC, CPVC, clear, and industrial.

There are two types of swing check valves we should focus on:

• Top Hinged – In this swing check valve, the disc is attached to the inner top of the valve by a hinge that allows the disc to open and close.

• Swashplate – This swing check valve is designed in a way that allows the valve to open fully and close quickly at lower flow pressures. It does this using a spring-loaded dome-shaped disc to allow the valve to close faster than a top-hinged valve. Additionally, the disc in this check valve floats, so liquid flows on top and bottom of the disc surface.
These types of check valves are most commonly used to prevent flooding in sewage systems and fire protection applications. They are used in systems that move liquids, gases and other types of media.

Lift check valve
Lift check valves are most similar to globe valves. They use pistons or balls instead of the discs that rotary check valves use. Lift check valves are more effective at preventing leaks than swing check valves. Let’s take a look at these two lift check valves:

• Piston – This type of check valve is also known as a plug check valve. It controls fluid flow in piping systems through the linear motion of a piston within a valve chamber. Sometimes the piston has a spring attached, which helps it stay in the closed position when not in use.

Clear PVC Ball Check Ball Valve • Ball Valve – Ball check valve operates simply using gravity. When there is enough pressure in the fluid, the ball is lifted up, and when the pressure is reduced, the ball rolls down and closes the opening. Ball check valves are available in a variety of material types and style types: PVC: clear and grey, CPVC: true joint and compact.

Lift check valves are used in many applications in many industries. You’ll find them in residential and industrial settings. They are used in the food and beverage industry, the oil and gas industry, and the marine industry, to name a few.

Butterfly check valve
The butterfly check valve is unique in that its disc actually folds in the middle to allow fluid to flow. When the flow is reversed, the two halves reopen to seal the closed valve. This check valve, also known as double plate check valve or folding disc check valve, is suitable for low pressure liquid systems as well as gas piping systems.

Globe check valve
Shut-off check valves allow you to start and stop flow in a piping system. They differ in that they also allow you to regulate traffic. A globe check valve is basically a check valve with an override control that stops flow regardless of flow direction or pressure. When the pressure is too low, the check valve automatically closes to prevent backflow. This type of check valve can work using an external control rather than an override control, which means you can set the valve to the closed position regardless of flow.

Globe check valves are most commonly used in boiler systems, power plants, oil production and high pressure safety applications.

Final Thoughts on Check Valves
When it comes to preventing backflow, there is no option but a check valve. Now that you know a little about the different types of check valves, you should be able to decide which one is best for your application.