PH Minus -
Hot tub chemicals

pH minus is used to reduce the levels and is tested using pH test kit which uses phenol red tablets in a comparator tube. It is difficult to predict how much acid will be required to reduce the pH to a precise level as it depends on what else the water contains but we suggest adding 50 grams for every cubic metre (220 gallons) and then re-test after 12 hours and re-dose if necessary.

Why is pH an important factor?

• pH minus is sodium bisulphate
• Sanitisers become less effective at killing bacteria as the pH rises
• As pH rises the water become more alkaline
• To keep the chlorine working it is recommended that the pH is kept below 7.6
• Bromine is effective at pH between 7.2 and 8.2

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