The Complete Guide to Alkalinity (TAC) in Swimming Pools: Insights and Applications
Understanding Alkalinity: TAC and Water Balance
Alkalinity, measured by the Total Alkalimetric Title (TAC), indicates the concentration of bicarbonate ions in your pool water. This parameter is essential for stabilizing the pH and preventing significant variations that could affect both the structure of the pool and the comfort of swimmers.
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Advanced TAC Measurement Techniques
In addition to the reactive strips and electronic testers previously mentioned, alkalinity can be measured by:
- Photometer with Alk test pill: Provides an accurate reading by reacting with the water to indicate the TAC.
- Graduated test tube with TAC test pill: A classic method that uses reagents to determine alkalinity.
- Drop counting method: Involves progressively adding reagents until a color change indicates the TAC level.
- AquaChek strip: Simple and fast, this method provides an immediate estimate of alkalinity.
The Direct Impact of TAC on Water Balance
TAC directly influences the stability of the water's pH. In a pool with a TAC of 25°f and a pH of 7.2, any addition of acid (decreasing the pH) or any natural reaction increasing the pH will be moderated by bicarbonate ions. This buffer mechanism prevents abrupt variations and maintains water stability.
Example Situations:
- pH Increase: Natural acid consumption slightly increases the pH, while the increase in TAC compensates for this rise, thus stabilizing the balance.
- pH Reduction: Manual introduction of acid reduces the pH, but bicarbonate ions absorb part of this acid, limiting the drop in TAC and stabilizing the pH.
Managing High TAC
A high TAC can lead to complications, such as a constantly high pH or cloudy waters due to the precipitation of calcium carbonate. Specific adjustments are required:
- To reduce TAC: Use concentrated hydrochloric acid or sodium bisulfate to delicately adjust the TAC, monitoring changes in pH and TAC after application.
Consequences of Low TAC
Low alkalinity means a lack of buffer effect, making the pH extremely sensitive to external changes. For example, the same amount of acid can cause a much larger drop in pH in water with low TAC than in water with balanced TAC.
Methods to Increase TAC
To adjust the TAC upwards, use:
- Anhydrous sodium carbonate or hydrated,
- Sodium bicarbonate,
These substances, by increasing the TAC, can also raise the pH, which will need to be corrected later.
Recommended TAC Values
Depending on sources and local conditions, the ideal TAC generally varies from 10 to 30°f. The optimal values are often between 10°F and 20°F for most pool waters, maintaining an effective buffer capacity without causing the inconveniences of excessive alkalinity.
Continuous Monitoring and Adjustments
Changes in TAC, whether natural or induced, must be closely monitored to maintain a safe and pleasant swimming environment. TAC corrections are not frequent but are essential after filling a pool or in the presence of significant imbalances. Use connected technologies and precise measurement methods for optimal management of alkalinity in your pool.
