Different Types of Check Valves: A Complete Guide

Different Types of Check Valves

The basic function of a check valve is to prevent backflow of fluids. However, different systems have different flow conditions, pressure levels, and operating requirements. That’s why not a single check valve can perform under all these conditions. To meet these needs, check valve manufacturers have developed some types of check valves. Those types differ in design and operation. So let’s dive in and discuss the most common types of check valves and their uses. 

1- Swing Check Valve

One of the oldest types of check valves is the swing valve, which allows fluid to flow in one direction. It automatically stops the fluid from flowing backward. The valve gets its name from the way its internal disc moves. Actually, inside this check valve, there is a hinged disc that swings to open and close. When the fluid is flowing in the right direction, its pressure pushes the disc away from the seat. As a result, fluid flows without resistance. 

However, if fluid tries to flow backward, the reverse pressure pushes the disc back against the valve seat. This completely stops the backflow. What makes the swing check valve stand out more is its simple design. Even if you are a beginner, you can easily install it yourself. However, the swing valve also has some shortcomings. As I said above, the disc movement depends on gravity. So it might take time to come to its original position when the fluid moves backward. This slow operation can cause problems in fast-moving fluid systems. 

2- Lift Check Valve

Another type is a lift check valve that prevents backflow by using a movable disc or piston inside the valve body. Unlike the swing check valve, it does not use a hinged disc that swings. Instead, it contains a disc that moves up and down. When the fluid is in the right direction, the disc remains upward, allowing the fluid to pass through the pipe. But if the fluid moves backward, the disc immediately descends to the valve seat. 

It sits tightly against that seat and completely prevents the fluid from passing. As the disc moves directly onto the seat, it creates a tight seal when closed.  That’s why it is best for situations like boiler plants and chemical processing facilities, where fluid leakage is a major concern. However, fluid must push the disc upward before it can flow through the valve. This can result in a higher pressure drop, which is a drawback of the lift check valve. 

3- Ball Check Valve

A ball check valve is a type of check valve that uses a round ball to control fluid flow. Its main purpose is the same as that of other check valves: to prevent backflow. However, it does this differently. Actually, inside the ball check valve, there is not a disc but a moving ball. When the fluid flows in the correct direction, this ball remains lifted, and the flow path stays open. 

But if fluid flows in the wrong direction, such as backward, its pressure will immediately move the ball. Now it will come and sit against the valve seat and stop the fluid flow. This ball also creates a good seal, so there is no chance of the fluid leaking. Besides, ball check valves can also handle fluids with small solid particles without affecting the valve.

4- Dual Plate Check Valve

A dual-plate check valve, also known as a double-door check valve, is one of the most special check valve types. Here, the valve contains two spring-loaded plates that work together to prevent backflow. How? Actually, when the fluid flows properly, the plates fold inward toward the valve’s center. This plate movement creates an unobstructed space for fluid flow. 

But when the flow slows down or stops, the spring attached to the plates quickly pushes them back toward the closed position. Now they are in a sealed position and do not allow the fluid to flow backward. This rapid opening and closing of the plates makes these check valves more convenient. This helps reduce the risk of water hammer. It is a pressure surge that can occur when fluid changes direction suddenly. But remember the dual-plate check valve has a complex design, so its installation requires skills and time. 

5- Wafer Check Valve

A wafer check valve is a compact, lightweight type of check valve compared with other types. The term “wafer” refers to its thin design. Actually, unlike many traditional check valves, a wafer check valve fits between two pipe flanges. With this design, there is no need for extra installation space, allowing it to fit into tight pipelines. Inside the wafer check valve, there might be spring-loaded plates or a single disc that opens and closes. . 

Now, as with other types, when fluid tries to flow backward in the system, the wafer valve disc will come against the seat. It will completely block the reverse flow and prevent damage to the system. Due to their compact design, you will often find wafer valves in water treatment systems, HVAC, and chemical processing plants. 

6- Silent Check Valve

In ordinary check valves, the valve disc waits until this reverse flow occurs before closing. Right? As a result, the disc closes forcefully, creating a very loud noise. To resolve this issue, a silent check valve came into the scene. In this type, the disc does not wait for reverse flow to happen. Instead, it starts closing as soon as the forward flow begins to decrease. 

This is possible because a spring is attached to the valve disc. When the flow is on the right side, this disc is opened. But at the point where the forward flow is decreasing, this disc immediately comes and blocks the backflow path. Now, when the disc is already closed before reaching the fluid, there will be no such loud shutdown noise. That’s where it gets its name from. 

7- Diaphragm Check Valve

Now, it comes to the diaphragm check valve, which uses a flexible diaphragm instead of a metal disc. A diaphragm is a thin, flexible sheet typically made of rubber or another elastic material. This flexible part is what controls the flow of fluid through the valve. Its working principle is very simple. When the fluid flows on the right side, the diaphragm remains upward, allowing it to pass. But when the flow slows down or stops, its pressure is not enough to keep the diaphragm open. 

That’s why it automatically comes to its original position and stops the fluid flow. Here, there is no need for an extra seat. Instead, the diaphragm itself acts as a sealing element. In addition to all this, the diaphragm can work well with dirty fluids. Some liquids contain small particles, mud, or debris that may cause problems for other types of check valves. But the diaphragm is highly flexible and resistant to contamination, so it does not deteriorate. This allows the check valve to operate under all conditions. 

8- Duckbill Check Valve

A duckbill check valve is another specialized type that uses a flexible rubber sleeve to control fluid flow. The end of this sleeve is just like a duck’s beak, which is why it is called a “duckbill”. Actually, it consists of a rubber tube that narrows and forms a flattened opening at one end. 

When no fluid is flowing, the two sides of the rubber opening naturally press against each other. As a result, the valve remains closed. Now, when it’s time to allow the fluid in the right direction, the pressure of the fluid forces the duckbill-shaped opening to spread apart. The fluid will start flowing. But if the flow slows or stops, the pressure holding the opening apart disappears. 

The flexible rubber automatically returns to its original shape. The two sides of the duckbill press together again, and no fluid can pass in the backward direction. Also, there are no metal parts in this check valve type, so it does not wear out due to moisture and lasts longer. That’s why they are used specifically in stormwater, sewage, and wastewater treatment plants. 

Factors to Consider When Choosing a Check Valve Type

As you can see, there are too many types of check valves. But not all those types fit every system. That’s why it is normal to get confused and make the wrong selection that causes problems later. To avoid this, here I will discuss some factors that you must consider before choosing a check valve type. 

• Fluid Type

First, know the nature of the fluid your system will handle. Not all fluids behave in the same way. Some are soft and less harmful, like water. But some contain chemicals that are very harsh and must be dealt with care. So always ensure the check valve type is compatible with the fluid passing through it. 

• Pressure Requirements

Every piping system operates within a certain pressure range. Right? So the check valve you choose must handle that pressure range. For example, if you are dealing with high-pressure fluids, you should go with dual-plate check valves. For a low-pressure system, ball and swing check valves are better. But make sure that the system has enough pressure to open and close the specific check valve.

• Temperature Conditions

Temperature can also affect your choice of a check valve. How? Actually, fluids can range from extremely cold to extremely hot. So the check valve you buy must handle that temperature. For instance, for very hot conditions, you should choose wafer, ball, and lift check valves. The diaphragm and duckbill valves will not perform here. They are generally good for cold to moderate temperatures.

• Flow Rate

The amount of fluid flowing through the pipeline over a given period is another factor to consider. If a large volume of fluid flows through the pipe, the check valve must be large enough to allow the fluid to pass easily. For such a high flow rate, diaphragm and dual-plate check valves are good options. For lower flow rates, small check valves like ball and swing will be enough. 

• Installation Space

Lastly, space available for installing the valve is also a critical factor you should not ignore. As you know, check valves come in different sizes. If you need the one for tight spaces, the wafer check valve is best for its thin design. However, where the space is big, you can go with a diaphragm, lift swing, or any other type. 

Conclusion

In many piping systems and industries, preventing backflow is a critical task. To make this possible, check valves play a major role. They contain a special inner design that allows the fluid to flow in only one direction. These check valves vary in design, use cases, and pressure-handling capabilities. This gives rise to different types of check valves.

In this guide, I have discussed the most common types of check valves and their specialties. You can see that each one has a different operating mechanism and stops the backflow differently. But the right choice among those depends on your project’s needs. So know the flow rate, space availability, pressure, and temperature needs, and choose the reliable one.