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Check Valve Fundamentals

Do you know what is the most important accessory of any pumping system? The answer is the check valve.

Many of you are already well-versed in understanding check valves, but it’s importance in water system control bears repeating.

The Basics

A check valve allows flow in one direction and automatically prevents backflow when fluid in the line reverses direction. In the home, check valves are found in the discharge line of the sump pump. They are also an important component of a submersible pump water system. Outside of the home, they are found in every building or industry where a pump is located.

Pump operation depends on how much water the pump needs to move at any given time. Improper pump cycling and eventual pump burnout happens when water continually flows back into the pump’s basin. Hence the need for check valves.

There are several types of check valves, including...

Swing check valve

The most basic design is the swing check valve, which features a simple design complete with a disc attached to a hinge at the top. As fluid passes through, the valve remains open. When a reverse flow occurs, the changes in motion as well as gravity help to bring down the disc, effectively closing the valve. Note: After the install, if no water goes through, then it is the wrong way around and must be reinstalled.

Spring check valve

These valves function in the same way as swing check valves, but the disc in the valve is held in place by a spring. When fluid pressure in the valve is higher than the pressure needed to open or close the valve, the spring lowers the disc to prevent reverse flow. In addition to protection against reverse flow, these valves also prevent water hammer (noise) and pressure surges.

Ball check valves

The ball check valves use a “ball” inside the body to control the movement of flow. When fluid is drawn in, the ball is pushed forward. When the fluid is pushed back, the ball is pressed into the round opening, which creates a seal and allows all fluid to flow out the second port in the intended direction. The ball can be spring loaded or free-floating.

Dual plate or split disc valve

A dual plate check valve is known as butterfly check valve or split disc. It operates with a door that is split down the middle and only folds one way to regulate flow. When fluid enters the valve, the pressure causes the hinges of the door to open. When flow is stopped the door is shut.

The above are just a few of the check valves available. While no one type of valve is good for all applications, each has its advantages and problems including noise (water hammer) vibration, reverse flow, sticking, leakage, component wear, or damage. Typically, these problems occur because the wrong style of check valve was selected for the application.

Before selecting a check valve, ask the Jim Murray Inc. team to review the application. As it is most likely in stock, we can quickly assist you with the best valve for your backflow prevention needs.

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