I'm considering replacing both my main circulation pump (1 hp Sta-Rite DuraGlas) and booster pump (3/4 hp, A.O. Smith motor, driving a Polaris 380). Flowmeter on return line shows a flowrate of 53 gpm. From measurements made a couple years ago, I had a pump suction pressure of -15" Hg and a discharge pressure (filter inlet) of 11 psig, for a Total Dynamic Head of 42.4 ft. I have no attached spa, water features. Just two 1-1/2" return lines and a return to drive the Polaris.
I believe the original circ pump was just a 3/4 hp and, for reasons long since forgotten, I replaced it with the larger 1 hp pump. Probably in response to the Pool Store's "bigger is better" mantra. The 3/4 hp booster pump is the original (rebuilt a couple times) seems like overkill as I need to add a return line flow restriction (pinched valve downstream from pump discharge) to keep from overdriving the Polaris.
So, I'm wondering if my pocketbook would benefit from smaller pumps (run longer, if necessary) in one, or both, cases. I've looked at the guide in poolplaza.com, but they don't provide info for the smaller size pumps. Would I benefit from a 2-speed or variable speed motor?
Any pump recommendations (or websites for sizing info) would be appreciated.