diy overflow

[mr.wilson]

I think you would need a 1" or 1.5" drain line to make something like this work properly. Yours appears to be 1/2" pipe, thus incapable of draining a significant amount of water. You may also need a gate valve rather than a ball valve for more accurate control.

Something like that should really be built out of clear pipe so you can monitor the accumulation of air bubbles see if it is primed properly. If you are on a budget, you could get away with having just one clear PVC pipe and the rest white.