Questions on changing to a 2 speed motor on a Hayward Super II pump

[keastman]

I am considering changing out the 2 Hp AO Smith motor( SF=1) on my Hayward Super II pool pump. The pool is in St. Augustine Fl and is not screened in. We have four large Live Oaks that surround it and this time of year it is a full time job just to keep the water a pleasant shade of brown or green from all the leaves, pollen, and calkings from the trees. I'm usually running the pump 18-24 hours a day for a month and the electric consumption is out of hand. In the summer I run it about 8 hours a day and 4 hours a day in the winter. I was hoping it would be more efficient to use a two speed pump on low 24/7 this time of year. The filter is a Hayward c1200 cartridge (120sq ft ?) I feel this pool is over pumped and underfiltered. The pool is 22900 gallons with a qwik clean II in floor cleaning system which does little with all the tree debris, also there is a spa that is approx 3-4' above the pool and a heat pump. At present the heat pump is broke and will not be replaced, and the spa isn't used. One other strange thing about this set up is that if I try to isolate either the main drains or the skimmer on the three way valve on the return, the pump will get air in the basket, but it does not as long as I have the valve set to both the main drains and the skimmer. The bubbles almost seem like cavitation from too much suction.

There is also a SWG (Jandy Aquapure) that is split off the main return on a separate 1 1/2" line that has it's return in the bottom of the skimmer housing with a reduction nozzle at the return in the skimmer so that it comes out as a strong stream. The return lines for the skimmer and drains are 2" and the equipment is about 45' from the pool at close to pool water level or a bit lower.

My question is, could I replace the 2 hp motor with a 2 sp 1 1/2 hp motor? I believe I read that I'd also have to replace the impeller if I downsized. Would I gain much electrical savings by down sizing the pump motor to justify the added expense of a new impeller and possibly diffuser? Or, would I be better off just getting a 2 sp 2hp motor? I'm also wondering how the SWG would fair on low speed especially since it is split off on it's own line from the main return.

Sorry for the long post. Thanks for any input on this problem you folks can give me. I've got pictures I can post of the set up but can't figure out how.

Thanks, Kevin