Bathing water that is low in pH can be corrosive to pool pumps, heat exchangers and damage the pool lining. pH plus is a powdered additive than can be used to raise the pH to a desirable level. However, too high a pH level and the effectiveness of all chlorine sanitisers starts to decrease. Always aim for a pH level of between 7.2 and 7.6. pH plus is suitable for use in swimming pools, spas or hot tubs. Swimming Pool Add 450 grams per 10,000 gallons of pool water. Dissolve in warm water in a plastic bucket and distribute evenly around the pool with the filter operating. Leave for 24 hours then re-test to ensure pH level is between 7.2 - 7.6. Spa and Hot Tub Add 11 grams per 1,000 litres of spa water. Dissolve in warm water in a plastic bucket and distribute evenly around the pool with the filter operating. Leave for 24 hours then re-test to ensure pH level is between 7.2 - 7.6.