So we had 12 inches of rain in 4 hours a few days ago.............never had the bubble before unless I had just opened the pump lid............noticed bubbles while it crested with rain.............drained the pool back to normal levels...............thought it was pump lid o ring (2 years old), so I replaced it.............NOPE........have no leaks throughout rest of VISIBLE plumbing..........sand filter doesn't have a pressure release valve, but has a gauge........should I release that? I want to say that I hear some gurgling in the upper part of the filter that wasn't there before...........any ideas? YOU ALL have ALWAYS come through in the past, so here I am again.....thanks in advance!