How to balance your spa water

Balance your spa water by taking into account 3 parameters: pH, alkalinity (TAC) and hardness (TH). It's important to achieve this balance, as it guarantees optimum efficiency of chemical products, preservation of equipment and perfect bathing quality.

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How can achieve a balanced spa water?

To know if your water is balanced, you need to regularly analyze three indicators in your spa.

pH on spa water

The pH value indicates the concentration of hydrogen ions. The pH scale ranges from 0 to 14: ideally, your spa water should have a pH between 7 and 7.4. .These are the optimum values for water disinfection. In other words, if the pH measured is slightly lower or higher (-/+ 0.4) than these values, there's no need to systematically resort to chemical treatment. Read our article All you need to know about pH for more information.

How to measure pH ?

To know the pH value in your spa water, there are chemical testers such as disposable strips or electronic ones like the pH meter or connected pH probes like ICO SPA. The reliability of the results depends on the pH tester you use. To find out more, you can read an article comparing the pH testers available on the market.

Modify pH in my hot tub

  • My pH is too high: add pH- containing an acid product, such as hydrochloric acid or sulfuric acid. Dissolve it in a bucket of water beforehand (to avoid damaging spa surfaces), then add it very gradually in small quantities. Take another pH reading after a few hours.
  • My pH is too low: Add pH+, which contains an alkalizing agent such as sodium bicarbonate or sodium carbonate. Dissolve your product in a bucket of water before mixing it with your pond water and add it very gradually.

Spa water TAC

The TAC (Titre Alcalimétrique Complet) measures the concentration of carbonate and bicarbonate ions to determine the alkalinity of the water. This measurement indicates the water's capacity to absorb pH fluctuations and stabilize it. The unit of measurement for TAC is the ppm (part per million) or the French degree (°f), and it should vary optimally between 80 and 120 mg/l. By regulating your water's TAC level (TAC+ or TAC-), you can "buffer" your water. All about water alcaninity.

Finally, you should know that when your spa is drained quarterly, the TAC increases naturally (up to 220 mg/l), then stabilizes naturally as filtration is activated. So there's no need to intervene to correct the TAC in the first few hours.

How to measure TAC

Water alkalinity can be measured with colorimetric strips or with electronic testers (photometers) used by professionals. Measuring TDS with a dedicated probe (Total Dissolved Solids in Water) is recommended, as it will give you the value of all the ions present in the water - including TAC. Everything you need to know about TDS, TAC and TH.

Correct alkalinity levels

  • Increase alkalinity use baking soda or sodium carbonate. Follow the product label for dosage instructions.
  • Reduce alkalinity: If the TAC is slightly elevated, filtration to oxygenate the water for several hours may be enough to rectify the problem. When water filtration isn't enough, you'll need to use sodium bisulfate. As these products are very powerful, you must wait 24 to 48 hours before swimming.

Water TH

The hardness of water is called TH, and refers to the concentration of calcium or magnesium ions. It is measured in French degrees (°F) or in ppm. The ideal TH is between 10 and 20°F (100 or 200 mg/l or ppm). The higher the TH, the harder and more calcareous the water. Conversely, the lower the TH, the softer the water. All about water hardness.

How to measure TH?

 Colorimetric bands for TH are commercially available.

Rectify TH

When the water is too soft (TH is low, below 10°f), first adjust the pH using TH+. You can also use calcium hypochlorite. Finally, activate your spa's filtration cycle. Finally activate a filtration cycle for your spa.

If the water is too hard (high TH, above 20°f), correct the pH with pH- then activate filtration. You can add a lime sequestering product to slow down lime formation.

Water balance depends on the use of your spa

The environment of your indoor or outdoor spa has a direct impact on water quality. The number of bathers and the frequency of spa use also impact water quality.

Firstly, you need to adapt the number of tests to the external factors involved in controlling the quality of your spa water. If you use your spa regularly, you should measure the parameters at least twice a month. Secondly, regular maintenance of your spa is essential to maintaining water quality and preserving your equipment. 

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ICO SPA aide équilibrer l'eau du spa en analysant le pH , l'ORP et le TDS de l'eau.