My 26"sand filter leaks intermittenly at the base. I have replaced the o-ring with a new one. this didn't help. I put o-ring lube on the new o-ring, this didn't help. Removed multi port valve again and checked for possible small cracks. Didn't see any. I tryed to tighten the lock ring down more, but its still will leak. Ist can go for a couple days and not leak, then start leaking again. My filter is running 19 lbs pressure on high speed. Welcome any ideas from all. Thanks