I've never been able to figure it out how many gallons my pool actually holds, so this weekend I tested the CL at 2ppm with the FAS-DPD, added 2 quarts of 6% and it rose to 4.5ppm. I tried to get the bleach calc to work backwards for me, but it wont. How do I figure this out? It's a 15 x 30 AG and I've heard so many different amounts of what it holds that I just thought I'd measure the rise after adding. Thanks.