Marina Plastic Check Valve

A check valve is the cheapest insurance in the hobby: it lets air travel from the pump to the tank, and stops water travelling the other way.

Key features

• The one-way action blocks back-siphoning, so a pump that is switched off or that fails cannot let the tank drain itself down the airline and onto the floor.
• It protects the pump as well, since water reaching the diaphragm will finish it.
• Fits inline on standard airline tubing — cut the line and push a valve onto each cut end.
• Directional by design: if the air stops as soon as you fit it, turn the valve around.

This matters most whenever the pump sits below the water line, which covers anything standing on the floor or inside a cabinet — a common setup, and an easy one to overlook. Fit one per airline, and glance at them occasionally, because they do eventually stick. Tubing, air stones and control valves are all in Aeration.