When clean my inlet filter pressure is 10 psi and I usually backwash when it hits 16 psi. After backwashing I add 1.5 cups of DE to bring the pressure up to 11 psi. Several days ago the inlet pressure was up to 15 psi when the pump turned off for the day. The next morning when the pump came on the inlet pressure was 11 psi? I watched it off and on all day and the pressure slowly came up to 15 psi before the pump shut down after 8 hours. Next morning when the pump started the pressure was again 11 psi and came up to 15 after 8 hours before shutting down.
This scenario has been repeated 4 days in a row - pressure rises to 15 then after setting overnight it is 11 psi the next morning. The gauge is fairly new seems to be working. I believe the 11 psi number because the polaris 280 cleaner moves around like it is getting adequate flow. At 15 psi it moves much slower.
The filter seems to be working like it should because the water is clear as clean glass. Anyone have any ideas what could be going on?