The valve that used to prevent backflow in a piping system is known as a Audco Check Valve. It is also known as a Audco Non-return valve or NRV. The pressure of the liquid passing through a pipeline opens the valve, whereas any inversion of stream will near the valve. Audco Check Valve Disc Type, or one-way valves, are designed to stop backflow and, ultimately, to protect pumps and compressors. They are available in several sizes and styles, from 1/8 inch to as large as may be required. Audco Swing Check Valve is probably the most common check valve in use today and is a full-port design, meaning the disc, when fully open, is out of the flow stream.