All about water alkalinity (TAC)

The alkalinity of water, also known as TAC (Titre Alcalimétrique Complet), is an essential element in the balance of water, along with the pH and the TH (water hardness). Measuring the TAC indicates the concentration of carbonate, bicarbonate and hydroxide ions in the water. A well-balanced alkalinity determines the “buffering” capacity of the water, and has an impact on the stability of the pH and acidity of the water.

What are the TAC targets?

The TAC should be between 100 and 200 mg/liter depending on the treatment used in your pool or spa. At the beginning of the season it should ideally be between 100 and 150 mg/l.

what are the consequences of a too low or too high TAC ?

• When the alkalinity of the water is too low (<to 100 mg/l), there is no "buffer" effect. The PH yo-yo's. Thus, the pH, responsible for water disinfection, no longer acts and the measurements are very unstable. The water becomes irritating for the skin and eyes and aggressive for the equipment. The water degrades rapidly.
• In contrast, if the alkalinity is too high (>250 mg/l), the water becomes cloudy and limescale deposits appear. This can damage your equipment.

The TAC regulation and stability are therefore very important, which should be checked regularly to keep the water healthy and clear.  If you encounter a pH problem, measure the TAC first and then the TH. This can save you the extensive and unnecessary use of chemicals. All about TDS, TAC and TH.

How to measure water alkalinity?

The alkalinity of water is measured with colorimetric strips or with electronic testers (photometers), used by professionals.

TAC in your pool

• In the spring , during the restart, the TAC is high due to water renewal (passive overwintering) and can reach 220 mg/l. En suivant les advices to restart your pool on spring , the TAC should drop back down naturally within a few days.
• In summer, check the alkalinity level (or TDS) once a month.
• In the fall, a lower TAC tolerance ( between 80 and 100 mg/l) can be tolerated.

TAC in your spa

• During each quarterly draining, the TAC will naturally increase (up to 220 mg/l) and then naturally stabilize with the activation of the filtration. 
• Check the alkalinity rate (or TDS) once a month.  

How to change the alkalinity level?

• Increase alkalinity use To increase alkalinity: use sodium bicarbonate or sodium carbonate. Refer to the product label for dosage instructions.

• To decrease alkalinity: If the TAC is slightly high, filtration to oxygenate the water for several hours may be sufficient to correct the problem. For high TAC, sodium bisulfate should be used. These products are very strong, so wait 24 to 48 hours before swimming.

• To get a good water balance, TAC and TH are crucial to achieve a pH balance, which acts effectively in the disinfection of water. all about pH