I am looking into a 27' round AGP. At 54 inch wall height it has approximatley 17,000 gallons. I do not plan to have any additional water features other than solar panels at the ground level near the pool. Initially I will use a manual vaccum (kids) but may switch to an auto cleaner eventually (kids refuse).
I am assuming that the pool will come with 1.5" flexible piping (Do I have choice?). I plan on using a 21 or 22inch sand filter. With that equipment, it appears that the minimum gpm is 36 gpm for an 8 hour turnover. The maximum flow for the filter is about 50 gpm. The 1.5" piping has a maximum flow rate of about 42-44 gpm.
I am assuming that the head on the AGP will be around 30 feet of pressure (from what i have read), and that the solar panels will not effect the head pressure much becasue they are at the same level as the pool.
I can get a .5 hp pump that will push 33 gpm. A .75 hp pump that will push 45 gpm @30feet head, and 30 gpm @ 40 feet of head. The .5 hp seems too small. The .75 seems about right, assuming the solar panels reduce the flow/increase the head a little.
Would I benefit from a two speed pump? I can get a 1hp 2spd pump that pushes 75 gpm hi speed, and 38 gpm low speed, or a 1hp 2 spd pump that pushes 68gpm hi speed and 34 gpm low speed. My question is, what do I need the high speed for? Either pump at hi speed will exceed the max flow rate of the sand filter. Is that a problem? Will manual or auto vaccuums work at 35-38 gpm?
Would one of these 1 hp 2 speed pumps, running at low speed and pushing 35 gpm, cost less to operate than a .75hp single speed pump pushing 45 gpm or slightly less?
The pumps that I am referring to are the Hayward Powerflo II .75 hp single speed, Hayward powerflo matrix 1 hp 2 spd, and a Pentair Dynamo 1hp 2 spd.