I have an old Pentair Purex 2000 DE pool filter. It's certainly not the best but it works and I have serviced it myself for years.

I have had difficulties, on occasion, getting the top cap over the O-ring but somehow I always manage. This time no dice. I just cannot get it over the swollen o-ring. I purchased a new redline o-ring and the top cap went on no problem. After clamping the filter up and charging the system the top cap leaks significantly.

The new o-ring is in good condition, just not sealing properly. Has anyone else had this issue and what was your solution. And no, buying a new filter system is not an option at the moment.