A clack valve is a mechanical apparatus that allows fluid to flow from one direction while at the same time preventing the fluid from flowing back the other direction. The basic mechanism for a clack valve involves an object that would both permit and obstruct the fluid whenever it flows from a specific direction. A clack valve achieves this by using a hinged valve that opens when upstream pressure from a fluid exceeds the minimum pressure required need to open it — also known as cracking pressure. The hinged valve makes a clacking sound whenever it closes due to fluid flowing from the opposite direction, hence the name "clack valve."
Clack valves are a type of check valve. They can be found most anywhere and perform numerous functions that are as varied as the materials of which they are made. When used for home or industrial purposes, clack valves can be made from plastic or metal alloy. A clack valve's function can range from regulating the amount of water coming out of a faucet to sealing a leak in a gas line to delivering oil in a pipeline.
Even the human body contains some form of clack valves. Heart valves are made of human tissue and resemble flaps that help move blood along the blood vessels. The valves play a vital function by preventing blood regurgitation — a condition where blood flows backward, which can be deadly if not properly treated.
Clack valves tend to operate independently from human control, which is ideal for continuous fluid surge. There are times, however, when they are needed to be used to regulate fluid flow. For this purpose, clack control valves are used.
A clack control valve is different from regular clack valves because of the way the valves operate. These valves can be controlled manually or by using an automated machine. A controllable valve allows the operator to maintain a desired level of fluid from entering or leaving a container. It also helps regulate the speed and flow of a fluid flowing through a pipe.
One particular use for clack control valves is for water softening. The process of water softening requires the use of either a brine or chemical solution. These reagents are use to "regenerate" the resins used to soften the water. By using clack control valves to regulate the flow of reagents, water softeners maximize the efficiency of the solution, minimize environmental impact, and conserve reagent use.