I'm a new owner of an in-ground pool and have only basic experience with an above ground pool, and I have an issue with my in-ground pool pump pressure.
While running, the pressure will be about 20PSI but when I turn the pump off for 2-3 seconds and back on the pressure drops to about 10PSI, but after 10-15mins the pressure is back up to 20PSI.
I've tried several backwash attempts. I switched from a 300LB sand filter to DE filter, no difference. I connected a hose from the filter outlet directly to the pool by-passing the pool piping. Still no difference. When I view through the clear plastic lid on the pump filter I can see the water flowing but that area isn't full of water when the pressure is high, but if I turn it off and back on it gets full and the pressure is low. So it appears the pressure goes up when less water is flowing, but I'm not sure why that would happen.
The pool is 20x40, any ideas or suggestions would be greatly appreciated.