So I have had this problem for about a year and one half. My filter basket has an air bubble in it, I've checked all the usual suspects and knew the leak had to be underground. No matter what I did I could not get rid of the air bubble, oh well it is what is is, so like I said I resigned to start digging this winter because it was getting worse. Well maybe some of you heard there have been multiple earthquakes here in CA, none of which were in my area. I am 350 miles away from the epicenter of the two largest quakes, but we felt both of them. The house rocked and the pool rocked. So today I put the pool filter on normal and payed no attention to it. Couple of hours later I go to drop the pump down one speed and I look in the filter basket, yep you guessed it, no bubble! As a matter of fact it was solid water! Not a smidgen of any air whatsoever! I couldn't believe it! So I'll watch it for a couple more days, but for now all I can say is Thankyou Mother Nature! LOL!!!