Noticed my water did not appear to be circulating. Backwashed the sand filter. When I turned the pump back on to Filter, the seal between the Praher Valve & the top of the sand filter popped, and water squirted out, under pressure, from the seal. Strainer baskets at pool and pump are clean. Am thinking I will have to disassemble the filter, laterals, and related parts. No reason I can think of for this situation to occur.

Input & suggestions would be appreciated.  Thanks!!