Little Giant check valves prevent water in the discharge line from draining back when the pump is not running. The check valve is a flapper-style, one-way valve installed in the discharge pipe of the pump. When the pump starts, the force of the water opens the flapper. This valve flapper then closes when the pump shuts off, therefore reducing the water force. The CV-10 check valve fits VCL-14, VCL-24, VCC-series, and VCMA-series condensate pumps and is for 3/8 in. vinyl tubing, 1/4 in. NPT.