Biorb non return valves are designed to prevent leaking water in the unlikely event of power cut by only allowing the air flow from the air pump to travel one way back siphoning of the aquarium water is not possibler the valve should be fitted six inches from the air pumpr suitable for use with all biorbsr at least every 6 months a check should be made by disconnecting the air pump and lowering the air line below the water line in the unlikely event of leakage a one way valve can be fitted