I can "hear" water swishing through the sand filter -- is that normal?
Also, is there a way to determine how much pressure I should be seeing with my setup? At 40GPM, I'm seeing about 14-15PSI. At 20PSI, I backwash. If I up that to 50GPM, it averages around 20PSI.
If I go to 75GPM, it averages 30PSI. I want to run at this rate but the SD80 maxes out at 35PSI.