Why monitor the pH of pool water?

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The pH of pool water is an indicator of the water quality and of its acidity level.
As water is a living medium, this acidity evolves according to external elements such as temperature, pollen, weather, or the number of bathers using the pool.

The pH must be regularly measured to ensure it is maintained within a certain range of values.
Monitoring the pH of your pool is a determining factor in water treatment and to ensure the best possible bathing comfort.

Stérilor explains everything.

What is the pH of a pool?

pH or hydrogen potential represents the concentration of hydrogen ions in the water.
This index serves to measure the acidity or alkalinity of the water.
The pH value varies from 0 (very strongly acidic) to 14 (very strongly alkaline).
The pH reference is defined by official standards.
The pH of pure water at 25°C is equivalent to 7.
If the pH is below 7, the water is considered to be acidic, while above 7.1 it becomes alkaline.


The ideal pH for a pool

For pure non-aggressive pool water that is suitable for bathing, the pH should be slightly alkaline.
The commonly accepted value is a level of 7.2, which corresponds to the value of human tears.

However, the pH of the pool water depends on the hardness of water which varies between regions, and also on the products used to treat and disinfect pool water.


The importance of correctly balancing the pH of your pool

Balancing the pH of your pool water is important for many reasons.
Firstly, an ideal pH ensures that water treatments are more effective by facilitating the disinfectant power.
In this way, chlorine is active at 60% at a pH between 7.2 and 7.4, but its efficiency falls to just 30% when the pH reaches 7.8.
In tangible terms, this means that too high a pH level limits the action of the treatment.

Furthermore, a poorly dosed pH encourages the proliferation of algae, resulting in green water and also limescale.
It also contributes to the deterioration of equipment (fasteners, liner, water filtration system, etc.).

Lastly, monitoring and balancing the pH of your pool water impacts the comfort of bathing for users.
An ideal pH is less irritating for the skin, eyes and mucous membranes of swimmers.


What can make the pH change?

Factors that can alter pH are multiple.
In particular:

  • A temperature rise in the water and/or the air,
  • External pollution such as pollen or dirt, etc.
  • Pollution brought in by swimmers: sweat, sun creams, etc.
  • Alkalinity (TAC) and water hardness (TH),
  • The carbon dioxide content,
  • Products used to treat water, especially disinfectants.


It is therefore primordial to regularly monitor the pH level of your pool water to ensure it remains within ideal values.
This will safeguard the quality and balance of the water, but also the efficiency of the treatments used.
You can use colour-based pH tests, analysis strips, electronic pH testers or a pH regulator, for automatic and optimised tests and regulation.