The rule is that one cubic foot of water contains 7.48 gallons of water.

http://www.montecitowater.com/how_ma...ter_in_a_c.htm

The best thing you can do is start reading our stickied threads, but start first by going to our sister site, poolsolutions.com.

But take a water sample to a pool store and post the results...don't let them talk you into buying anything yet. Promise them you'll be back (you probably will).