From my bad memory. I believe the pressure started at about 25 and rose to maybe 35. But since I never really went by the gauge I can't be sure. I always went by the pressure I felt on the return. However, I had to backwash at least every other week and sometimes weekly. We never have a bunch of swimmers as it is only my wife, daughter and myself. Friends on very, very few occasions. So the pool isn't being overused. If I didn't backwash that often the water would be slightly cloudy. Once I backwashed to would be clearer just never crystal clear. I kept it balanced all summer long with no problems. Sorry, I don't have the numbers as I trashed them at the end of the season. I was wondering if I had too much pump was it just pushing the dirt right through the sand? Thanks, again.