First establish the pH of pool water with a good quality water test kit. Determine the amount of pH minus needed. With your pool pump running broadcast the pH reducer of the deepest part of the pool. For shallow pools, dissolve in a pail of water before adding to pool. Always have your pool pump running when adding this chemical.
pH 7.8-8.0: 4 oz per 10,000 gallons of water pH 8.0-8.4: 8 oz per 10,000 gallons of water pH above 8.4: 12 oz per 10,000 gallons of water