Alkalinity of water



The alkalinity level, also known as TAC, is an essential element in the balance of the water along with the pH and TH (water hardness). It should be between 100 and 200 mg/l depending on the treatment used in your pool or spa. Ideally at the beginning of the season the alkalinity should be between ideal 150<TAC<200 mg/L

A good balance of water alkalinity determines the “buffering” power of the water, which impacts the stability of the pH and the acidity of the water. It is a very important parameter that must be checked regularly to keep the water healthy and clear. If you have a pH problem, measure the TAC +TH first. This can save you the need to use a lot of chemicals.



What consequences ?


When the alkalinity is too low, the pH, which is responsible for disinfecting the water, no longer acts. The water becomes irritating to the skin and eyes and aggressive to the equipment. It degrades rapidly.

On the opposite, when the alkalinity is too high, the water becomes cloudy and limescale deposits appear. Your equipment can then be damaged.

How do you measure alkalinity?



It is measured with colorimetric strips or electronic testers, used by professionals.

Other devices such as ICO Pool and ICO SPA measure the TDS (Total Dissolved Solids in Water) which includes the concentration of carbonates and bicarbonates (TAC).

Learn more about TDS, TAC and TH. 


  • In the spring, during the summering period, the TAC is high due to the renewal of the water (passive wintering) and can reach 220 mg/l. If you follow the summering instructions, the TAC should drop naturally within a few days.
  • In summer, check the alkalinity (or TDS) once a month.
  • In the fall, a lower TAC tolerance (between 80 and 100 mg/l) is acceptable.


  • With each quarterly draining, the TAC will naturally increase (up to 220 mg/l) and then naturally stabilize as the filtration is activated.
  • Check the alkalinity (or TDS) once a month.


How to change water alkalinity? 


    • To increase alkalinity: you can use sodium bicarbonate or sodium carbonate. Refer to the product label for the dosage.
    • To reduce alkalinity: If the TAC is slightly high, filtration to oxygenate the water for several hours may be sufficient to rectify the problem. For a high TAC, it is advisable to use sodium bisulfate. As these products are agressive, it is necessary to wait 48 hours before bathing.
    • To obtain a good water balance, the TAC and TH are decisive to obtain a pH balance, which acts effectively in the disinfection of the water. To learn more about pH, click here.




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