I purchase the bleach at Dollar Tree - Home Store Bleach. It does not state on the bottle but I would surmise it is 6% sodium hypochlorite. My pool is 20 x 44 - 30,000 to 35,000 gallons. I have used Clorox Concentrate a couple years ago and my pool started sudzing up. Someone on the forum told me that Clorox Concentrate should not do that but the Dollar Tree is the only place I can find regular bleach.