Wafer check valves are in-line piping valves used to control fluid flow direction and reduce or fully prevent possible back flow within plumbing systems. Wafer check valves are also known as clack valves, reflux valves, non return valves and one way valves. This valve type has been engineered to automatically eliminate the fluid flow reflux that can occur whenever a process system is shutdown. These valves feature a hinged, flap-like disk (the wafer) that is used to allow and restrict liquid flow. This disk only opens in one direction and closes shut under back pressure to seal the valve against opposing fluid flow. Wafer check valves require a minimum amount of system fluid pressure to operate. The check opens whenever upstream pressure is greater than downstream pressure and closes whenever downstream pressure exceeds upstream. Although at first glance this may seem like just a matter of space, the presence of a valve body, unlike the bare wafer check valve, makes a big difference in the valve’s functionality. As flanged check valves sit in place, there is not much room for the disc to open in the pipe. This means that flow in the check valve is often restricted. Wafer check valves, on the other hand, have a molded body that creates space for the disc to swing fully open, allowing full flow. As you can imagine, this is very important if your application requires full flow.