Our motor just died and we felt it would be a good opportunity to upgrade. We've gone through the calculations for feet of head and are more confused than ever. We currently have a 23,100 gallon pool with a Pentair Pinnacle pump and 1.5 hp AO Smith Centurion motor (dead) which runs (ran) at 3450 rpm. Is there a simple way to estimate what size variable or two stage pump would work for our situation? We have about a 75' run of plumbing to both the main drain and the skimmer. An online customer service person at a very reputable online company told us that we needed a 3 hp variable speed pump. Also, with no water features, heater, fountain, etc., would we benefit from a variable speed over a two speed pump, or even another single speed, pump? Thanks all!