1The bottom valve, also known as the check valve, is a low pressure flat valve . 2The pump is to ensure that the liquid flows in one direction in the suction line, allowing the pump to work properly. 3When the pump stops working intermittently, the liquid can not be returned to the water source tank, and the suction pipe is filled with liquid to facilitate the start of the pump. 4Adopts high quality PVC material which can withstand long time working in water. 5Professionally and practically designed with good working performance.Features:The bottom valve, also known as the check valve, is a low pressure flat valve . The pump is to ensure that the liquid flows in one direction in the suction line, allowing the pump to work properly. When the pump stops working intermittently, the liquid can not be returned to the water source tank, and the suction pipe is filled with liquid to facilitate the start of the pump. Adopts high quality PVC material which can withstand long time working in water. Professionally and practically designed with good working performance. Specification:Item Type:Pump Foot ValveMaterial:PVCColor:BlackType: 1.5in 2in 2.5in 3in 4in(Optional)Package List:1x Valve