I have a 20x40 IGP vinly pool finishing completion. I have the hayward dual speed super pump along with a DE filter. When the pump is in high speed my pressure is currently at 10 (just backwashed a day ago because of dirt in pool after rain and testing the backwash feature). When I switch the pump to low speed the pressure reading drops to 0 but water is still going through the filter as I can see debris moving in the pump strainer basket, skimmers as well as feel it coming out of the returns in the pool, although at a lower rate than when on high speed. My question is, should the pressure reading on the filter be at 0 when I switch the pump to low speed? The whole system has only been running for a week.