A Non-Return Valve allows liquid to flow in one direction only. The valve is only opened when there is a flow of water, thus if the flow stops or if there is a back flow of water the valve closes. The spring check non return valve can be used vertically, horizontally or in oblique angles; an arrow is stamped on the body to indicate the direction of flow. Valves are available with both female BSP threaded connections ranging in size from ½” through to 2” and with Irish size compression connections ranging in size from ½” – 1” on either side. A stainless steel strainer is available separately which allows the non-return valve to be also used as a foot valve.