I have an AO Smith 1.0HP pump with an SF of 1.40. I don't know how to calculate all the suction and return head stuff, so I just used the rough estimate of multiplying 2.31 x 17psi (from the gauge on my filter after backwashing) = 39.27. According to the pump chart that would be 65gpm but my filter is only rated at 52 so I used 52gpm. My pool is about 30,000 gallons and that comes out to be 9.6 hours for one turnover. So, two would be 19.2 hours which is pretty close to 24/7. Did I do something wrong? I was trying to determine if I should install a timer and not run the pump 24/7, but for 5 hours I'm not going to worry with it.