In 17,500 gallons of water, each 2.5 quarts of 6% chlorine should give you just over a 2 ppm chlorine rise. There are a couple of pool calculators you can use--one is www.thepoolcalculator.com, and the other one is Bleachcalc. I prefer Bleachcalc for ease of use, but I have it set on my desktop so I'll have to look around the forum for the link to it. When I find it I'll try to come back and post it here.