A couple of times a week I notice a gurgling sound when the pool turns on and have some bubbles coming primarily out of one of my 5 returns. I have to go to the filter canister and crack the valve on top to let the excess air out and then everything seems good for a few days. Everything else seems to be in good condition, can't see anything leaking or any wet spots. I'm keeping the pool full so it's not getting lower than the skimmer and sucking in air.
The pool is 5 years old so not sure what to do to try and find out what is causing this problem. I did notice a few drops coming out of the valve on top of the filter canister the other day, could that be the problem? Everytime I check the equipment it seems to be OK.
Any ideas on what to check or look for?