New 5ft tall cylinder tank and the overflow had the gurgle issue. I read about the Durso standpipe to remedy the issue. Made one out of 1.5 PVC
and put in adjustable air valve on the top (opens to about 3/8 max). This definitely made it better, but I'm still seeing some issues. Every minute or so I see the water level in the tank drop a bit, the top of the Durso (where the air valve is) makes some noise. After a couple of seconds, the water level goes back up and the sound is gone. Not sure what I need to do to adjust. I opened the air valve all the way. If I close the air valve any, it doesn't work at all. Any ideas?