PVC overflow air valve ?

[khanhnguyen99]

Hi,
I want to build an PVC overflow and found on YouTube most of them had air valve at the top on the intake.
1. What is the function of the air valve?
2. What air valve can I use? Where to buy?
Thank you very much for you advice.

Khanh

[Rybren]

The air valve is typically used suck out air that accumulates at the highest point of the overflow.  People attach one end of an air hose to the valve and then attach the other end to a powerhead or aqualifter so that the air gets sucked out.  If too much air is allowed to accumulate, the overflow will fail and a flood will occur shortly thereafter.

You can pick up the air valves at most LFS in the area.

[khanhnguyen99]

Thank you very much.

[Rybren]

You're welcome - just ask for an airline check valve at the LFS.