Check Valve Fish Tank Aquarium Air Pump Silicone Non-Return One Way Airline Pump  | Aquarium Store | Fish Tanks | Fish Bowls
 
 
A Non-Return Check valve is an essential accessory when setting up an air pump for your aquarium. Due to gravity water will always try to find its own level, which means that if your air pump is placed lower than the water level, you risk flooding in the event of a power outage.

The addition of an inexpensive one-way non-return check valve can save you all the hassles of your aquarium flooding. They are designed to only allow flow in one direction, therefore they allow the pump to push air to the aquarium but do not allow water to flow back from the aquarium to the pump.
 
Specification:
Colour:Red/Black/Blue
Quantity：5/10 pcs
Fits Hose: 4mm