Protects against dirt. Connect the suction filter to the 25 mm (1") suction hose sold by the meter (Art. No. 1721-22). It protects against dirt and thus damage to the pump. The check valve shortens the suction time, allowing for more efficient pumping. Complete with hose clamp for easy attachment. Check valve. The check valve significantly shortens the suction time after shutdown, allowing for efficient pumping. Supplied ready for connection. The suction filter can be easily connected to the suction hose (sold by the meter); the connection is vacuum-sealed. Completely ready for connection. Complete with hose clamp for easy attachment.