PH Minus is a granular acid used for lowering the pH if it rises above 7.6
All chlorine based sanitisers become less effective at killing bacteria and viruses as the pH rises ( becomes more alkaline).
Acid/Alkaline conditions are measured on the pH scale which ranges from 0 – 14. Ideal bathing conditions exist at a slightly alkaline level of 7.2 to 7.6 with Total Alkalinity of 80/140 mg/l (ppm).
pH Minus is used to reduce the pH level of your spa/pool water when it goes above 7.6, it can also reduce Total Alkalinity of your spa/pool water.