Water does not appear to be filtered very well

[PoolDoc]

13K gallon => 8 hr turnover min = 27 gpm

21" sand filter 15 gpm/sft max flo for good filtration => (0.88' radius x 0.88 x 3.14) = 2.14 sft / 2.14 x 15 = 36 GPM

Possible options:
+ 1 HP 2 speed 240V Super Pump:
http://www.a1poolparts.com/-strse-84...eed/Detail.bok
(oversized on high, but run it on low except when backwashing or vacuuming - built in toggle switch)

+ 3/4 HP 2 speed 120V Pentair Whisperflo WDFS-3
http://www.a1poolparts.com/-strse-61...ump/Detail.bok
(oversized on high, but run it on low except when backwashing or vacuuming -- requires time clock or external toggle switch)

+ Hayward SP15922S Power-Flo Matrix Above-Ground Pump 2-Speed @ Amazon

That will give you a place to start shopping. The first two are in ground pool pumps, and will last longer, be more efficient, but cost 2x as much. Please note that the first pump is 240V only, which probably would require new wiring. My recommendation is that you NOT purchase a pump from a local store. Instead, if you do the installation yourself, buy online from someone reputable (like A1 or Amazon) with a DEFINITE physical return address. OR, if you hire it done, let your installer make the purchase from SCP (wholesaler) in Chattanooga or Atlanta. Your installer will get a price about as good as a pool store, but will have to stand behind it, if he bought and sold it. Otherwise, online prices will be substantially cheaper.

My choice, for your pool, if the budget is not a big issue is the 115V 2speed 3/4 HP Whisperflo. But, I'll as mas985 to look at this, and see if he has another recommendation.