Our 20K in-ground pool has a Hayward pump and sand filter. Had a heater installed last year and all the pool house piping was replaced. We uncovered the pool yesterday, drained some excess water so the skimmer would work, threw in some chlorine tablets so algae wouldn't bloom, and figured on adjusting the chemistry starting today. We left the pump on continuously - pressure was normal. The heater was not on and won't be until the chemistry is correct.
In the morning the pool house was flooded and 30% of my water gone from the pool - down about a foot. The output pipe at the top of the filter had separated from the threaded hole in the filter. I can easily slide the threaded pipe in and out of the opening - it looks to my untrained eye that the original PVC pipe thread was 1-2 mm too small. There is no damage or irregularity to the threads on either the pipe or the filter. I was furious, thinking the contractor used the wrong size pipe and jerry-rigged it with a gasket fitting.
When I called the contractor, he says "oh yeah - the system had a blockage and the water in the pipe overheated - the PVC shrank and the fitting popped off." This sounds like total B.S. to me. If there was a blockage, why did the blockage magically go away and the pump continue to empty 30% of my pool? Why would the filter output coupling fail, instead of the pump fitting which is where the heat would collect? Has this happened to anyone, and was the explanation plausible? I'm thinking this is just a fabrication to cover poor installation technique.