A one-way valve, also known as a check valve, clack valve or non-return valve (back flow valves), is a mechanism that only allows fluid to flow through it in one direction.  They have many applications in construction and plumbing, but for this article we will be discussing their use in the prevention of backflow.

A one-way valve actually has two valves, or openings, in the body of the mechanism, one for fluid to enter and the other for fluid to leave.  The valves are designed to operate under a specific fluid pressure, and if that pressure is not detected the valve will shut down and not allow fluid to flow.

This has important ramifications in the case of backflow in plumbing systems.  Backflow occurs most often when there is a sudden drop in water pressure from the source of a water supply to the end-point of that water flow.  In other words, in a city water system, if the water pressure drops from the source of the potable water supply to the home or business, then back flow can happen, and that means water will reverse direction and contaminated water will flow back into the city’s potable water supply.

To prevent this from happening, one-way valves are used. When the water pressure drops the valves shut down and do not allow contaminated water to reverse direction.

There are various types of one-way valves.  The ball check valve uses a spherical bal to block the flow when pressure drops.  The diaphragm check valve uses a flexible rubber diaphragm to stop the flow.  A swing check valve, also known as a tilting disc check valve, uses a disc which swings on a hinge to block the flow of contaminated water.  A stop-check valve has an override control that stops flow regardless of direction or pressure.  A lift-check valve uses a disc which lifts up and drops down depending on the degree of water pressure and an in-line check valve is similar to a lift check valve but works with a spring that will lift when pressure is interrupted.

Depending on the size of the water system, one or several of these one-way valves will be used.  The thing to note is that in the State of Texas, and in many other states, annual backflow testing is required, and it is required that a licensed backflow tester do the testing.

City Backflow Testing does affordable backflow testing for most cities in the Dallas/Ft. Worth Megaplex.  For the best in backflow prevention device testing and maintenance, call the folks at City Backflow Testing.