Noisy overflow

[tcermd]

I cannot figure out how to correct a noisy overflow. . The water level goes up and down 5 inches cyclically , and sometimes the herbie breaks siphon. My return pump is very strong and I did put a ball valve on it, and it doesn't matter how I adjust the return, there is no change. There is a screw top on top ofthe herbie to adjust air intake, but adjusting the screw top and air intake does not seem to change the level in the overflow, nor the constant up and down of the water level. Please help

 

[Flippers4pups]

Post a picture of the overflow and drains on the tank and the plumbing going to the sump please. This will help us here to see the possible problem area. Thanks

 

[tcermd]

Actually have never posted a picture. Is there a sticky?

 

[BrianKC]

A herbie shouldn't have an air intake. Definitely need pics.