Over the past 2 years I have had issues with Spider Gasket failure (5 times) - Pentair Multiport side mount 2" Sand.
I occurs over time after backwash, waste or rinse operations...
Before asking, YES to all below:
Turn off the pump before rotating valve
Always rotate in same direction
AND - absolutely depress handle fully/
The failure seems to be one (ore more) spoke(s) where the large diverter opening will allow the water to travel past (over) an exposed spoke. (Personally, I see it as a design flaw with the valve.)
When I am finished backwashing, pumping to waste, etc... eventually the gasket is pulled up and then allows water to pass to backwash when in filter (run) position.
Note - I have tried NUMEROUS adhesive techniques... Including the Blue ATV (manufacturer recommended) and vinyl patch repair adhesive (recommended by LPS)... Always completely clean before applying. Note also - I have tried magic lube on diverter plate to prevent sticking. Still ultimately fails.
I am wondering if the following may be a factor in the failure.
2 years ago I had a gas heater installed. There is a bit of science around lengths of pipe vs. #'s of elbows, etc. My CLEAN sand filter pressure moved from a 10 lbs of pressure to 15 lbs. I was told not abnormal. I am concerned that it is possible that there may be a GREAT DEAL of water turbulence at the point of entry to the Multiport Valve.... Beyond that, I am out of possible causes.... Any ideas appreciated!