I use a robot cleaner during the summer but we are using a Kreepy (suction) over the winter. This is our first winter and I am keeping our pool open since we don't get a lot of leaves etc. However, I have noticed that the pressure has been steadily climbing since we put our robot up. We have a TA100 (625 lbs) sand filter and a 1.5 HP uprated Whisperflo pump. Over the summer the normal operation pressure was 15 psi and we seldom had to backwash. Since we are now using the Kreepy, I am having to backwash more but can't seem to get the pressure back down to the 15 range. I just backwashed this afternoon and the pressure is 21. Opening/closing valves has no effect on the reading. I am wondering if I should be concerned about a blockage somewhere or maybe I am just not backwashing enough. Probably 5 minutes is the longest I have done it but the water looks pretty clear coming out of the hose. Thanks in advance!