How to balance your pool and spa water

High - pH

Probable Causes

  • Mains water has a naturally high pH
  • -pH drift due to sanitiser being used
  • Excess addition of Soda Ash (pH plus)

Regulating pH is one of the most important aspects of pool care and it should be maintained in the range of 7.2 - 7.6. High pH can result in cloudy water and contribute to scale formation. More importantly, high pH will reduce the effectiveness of the sanitiser as it will release less free active chlorine.

1. Effect of Mains water - the pH and alkalinity of your mains water will have a major influence on the water balance of the pool. It is therefore important to regularly check both pH and alkalinity of the mains water when refilling the pool or adding substantial quantity of fresh water.

2. Effect of Sanitiser - the sanitiser being used can have a significant effect on the pH. Of the chlorine based sanitisers in regular use, sodium hypochlorite (liquid chlorine) and calcium hypochlorite will tend to increase the pH.

3. Excess use of pH increaser / Soda Ash - it is important not to routinely add pH increaser (or Soda Ash) without testing the pool water. Carry out regular tests and only add the quantities of chemical indicated by the test.

Low -pH

Probable Causes

  • Mains water has a naturally low pH
  • -pH drift due to sanitiser being used
  • Excess addition of Dry Acid (pH Minus)

Regulating pH is one of the most important aspects of pool care and it should be maintained in the range 7.2 - 7.6. Low pH can lead to skin irritation and corrosion of equipment.

1. Effect of Mains water - the pH and alkalinity of your mains water will have a major influence on the water balance of the pool. It is therefore important to regularly check both pH and alkalinity of the mains water when refilling the pool or adding substantial quantity of fresh water.

2. Effect of Sanitiser - the sanitiser being used can have a significant effect on the pH. Of the chlorine based sanitisers in regular use, 'trichlor' based slow dissolving chlorine tablets are acidic and will tend to reduce the pH. The hard waters found generally in the South East of England will have a higher tolerance to acidic chlorine donors and will require less pH adjustment

3. Excess use of pH Minus - it is important not to routinely add pH reducer (Dry Acid) without testing the pool water. Carry out regular tests and only add the quantities of chemical indicated by the test.