help me silence the overflow!

[Ron99]

Originally Posted by smokinreefer

so, is that right?

More or less. The secondary line after the U acts as the emergency overflow. If you look at "herbie" overflows you can see how they are set up with 2 holes using a main drain controlled by the valve and a secondary drain You want to keep the bottom of the U part at about the level of the water in the tank so that little to no flow normally goes down that one. 95%+ of the flow will go down the primary line with the valve.

You need the valve to adjust the flow down the drain to math the flow from your return pump so that zero air is being drawn down that line. it is the air being drawn down that gurgles and is noisy. I have actually removed the air valve entirely as it was not really needed. I still have the small hole in the top ala Durso to vent air.