HuanZhong Duckbill Check Valves are precision-molded, one-piece elastomeric valves that provide reliable backflow prevention at low-pressure differentials. Our duckbill check valves allow free flow with positive differential pressure. With negative differential pressure, backflow is checked. Pressure drop across the valve is a feature unique to Duckbill check valves. They can be designed to operate in a few millimeters (inches) of water to several hundred kPa (psi), depending on valve size, geometry, and compound characteristics. Vernay Duckbill check valves are also designed to start functioning at specific opening and closing pressure ranges, depending on your specifications.