I have a Sta-Rite S8M150 and the filter is very efficient, but large for my 13,000 gallon pool. I want to get a Pentair VS pump so I can run longer on low speeds to save on the PG&E bill, but was told that because I have a large filter, I would have to run a minimum pump speed of 50GPM. Which means I would always have to run the pump at a higher RPM. Is this true?