Just found some 12.5% liquid shock from a big box store (BJs) here for 1.56 per gallon equivent to the 6%. Its 12.50 for 4 gallons of 12.5% so its equivelent to 8 gallons of 6%. That is the cheapest I have found around here. Costco has bleach for about 2.25 per gallon.