We are also looking into replacing our 1hp pump with a two-speed one. Don't know how old the current pump is. Here are the details: (1) 30,000 gal inground plaster pool; (2) sand filter with 325lb of sand, rated 60gpm; (3) challenger pac-fab pump at 1hp. I can find a pump curve on the web but am not sure what to do with it. Is a 1hp pump sufficient for this setup? I'm figuring the turn on the pool is 8.3 hours which seems too slow - but maybe I'm calculating wrong (?)