A check valve, also called a clack valve, non-return valve, reflux valve, retention valve or one-way valve is a valve that allows fluid (liquid or gas) to flow through it in only one direction to prevent backflow (reverse flow) through the piping system, appliances, or fixtures. Various types of check valves are used in a wide variety of applications and will often be found in common household items such as faucets, toilets, shower plumbing fixtures, and systems using the flow of water or gas.
Check valves are designed to work automatically. Since they are not operated by a person or by external control, they do not have a valve handle or stem.
Types of Check Valves
There are many types of check valves available for use in different applications. Depending on the use, you will find types such as ball, diaphragm, swing, clapper, stop-check, lift-check, in-line check, duckbill, and pneumatic non-return check valves.
Categorized Check Valve Types
Dual Plate Type
Stop Check Valve
A swing check valve or swing valve uses a disc that swings on a hinge or trunnion onto the seat to block reverse flow or off the seat to allow forward flow. Though they come in various sizes, swing valves are not designed for use in tight spaces like the wafer check valve. Most applications requiring a large check valve will use the swing variety. Swing check valves are the oldest and most common valve found virtually everywhere. Top hinged valves are often installed with gate valves because of the free flow they offer. Pipelines with a relatively low-velocity flow are what work best for these valves. A pulsating flow would virtually destroy the seating elements. Tilting disk valves maintain fluid opposition and turbulence at a manageable level due to its straight-across design.
The lift-type family is home to the piston and ball check valves. The piston valve is great for solving reverse flow issues you may encounter because the disk will be forced to close, which prevents the possibility of fluid entering in. The ball valve functions similarly to the piston, instead of a disc, a ball is used. The ball is the only moving part to prevent the possibility of reverse flow.
One of the most common check valve designs is the ball check valve. In this type, the closing member or movable part that blocks the flow is a ball. The ball may either be spring loaded to help keep it shut or in designs without a spring, the ball itself moves towards the seat to create the seal. The main seats of the ball check valve have a conical taper to guide the ball into the seat and form a positive seal.
Lift check valves are most often used for high-pressure service where the velocity of flow is high. The disk connects perfectly to the seat. Both horizontal or vertical pipelines are able to provide adequate upward flow. This type of valve prevents reverse flow. The gravity and backflow forced the disk downward to set on the seat when the flow reverses or stops. These valves are frequently used in piping systems that used globe valves as a control valve.
Check Valve Parts in Order from Top to Bottom
Check valves are can be found anywhere. They are found in multiple spots in homes—including but not limited to—bathrooms, kitchens, heating systems, and sump pumps.
When you need a check valve to prevent backflow, you'll find a complete line of valves at F.W. Webb. From ball, tilting disc, double door, nozzle, and swing, we have the check valve you need to complete the task at hand.
We carry bronze check valves, cast iron check valves, corrosion-resistant valves, and check valves made of ductile and alloy iron. You'll also find a variety of connection types including solder, threaded, flanged, wafer, grooved end connections. Our check valves greatly minimize water hammer noise with new technologies that will exceed your expectations.