1 The bottom valve, also known as the check valve, is a low-pressure flat valve. 2 The pump is to ensure that the fluid flows in one direction in the suction line, allowing the pump to work properly. 3 When the pump stops working intermittently, the fluid cannot be returned to the water tank, and the suction pipe is filled with fluid to facilitate the start of the pump. 4 Uses high-quality PVC material that can withstand long-term use in water. 5 Professionally 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 fluid flows in one direction in the suction line, allowing the pump to work properly. When the pump stops working intermittently, the fluid cannot be returned to the water tank, and the suction pipe is filled with fluid to facilitate the start of the pump. Uses high-quality PVC material that can withstand long-term use in water. Professionally and practically designed with good working performance. Specification: Item Type: Pump Foot Valve Material: PVC Color: Black Type: 1.5in 2in 2.5in 3in 4in (Optional) Package List: 1x Valve