All about water hardness (TH)

Une eau trop dure avec un excédent de calcaire est un danger pour les équipements des piscines et des spas. A l’inverse, une eau trop douce entraîne la corrosion des métaux et des parois. Voici nos conseils pour traiter efficacement l’eau de votre bassin et garder une eau équilibrée. 

The hardness of water is measured with the TH, responsible for the water balance.

How is water hardness measured?

The hardness of water is measured with the TH (Hydrotimetric Title), which corresponds to the concentration of calcium and magnesium mineral salts. It must be between 10°f and 20°f French (100 to 200 mg/l or ppm).

Below 10°f : the water is too soft, which can lead to problems with corrosion of metal parts and cements. To identify water that is too soft, do this simple test: take a sample of water from your pond and put it in a bowl. Try lathering it up with soap. The more foam, the softer the water and the less foam, the harder your water.

Above 20°f : the water is too hard. The water then becomes cloudy and milky. The limescale quickly deposits on the liner at the waterline and on the equipment (filtration, ladders and pipes). This hard water is also irritating to the skin and eyes.

How do you know if the water in your area is hard or soft?

It is important to know the quality of the water in your area and its hardness to monitor the water in your pool and spa. 

To obtain the hardness index of the water in your community, you can:

  • Consult the official water quality data on the Ministry of Health.
  • Go to the town hall, which should display this data.
  • Look at your water bill, the ARS of your region makes a synthesis of the water quality of your region annually and indicates it on this bill.

Which solutions to analyze the TH?

Before treating the water with the right dosage, you need to analyse the three main factors responsible for water balance which are pH, TAC and TH :

  • To measure TH, you can use suitable colorimetric strips available on specialized pool or spa stores.
  • Some of the latest generation devices, such as ICO analyses the TDS (Total Dissolved Solids), thanks to its conductivity probe which measures all minerals (calcium, bicarbonates) and trace elements (chlorine, bromine ....).
  • The TDS is between 250 and 2000 ppm for pools treated with chlorine or bromine, and between 3000 and 5000 for pools treated with salt.

How treating water hardness

with water that is too hard (above 20°f French)

  • First, monitor the temperature of your pool water. A high temperature promotes the formation of scale.
  • Secondly, regulate the pH of your pool (between 7.2 and 7.4 for a pool treated with chlorine).
  • Finally, you can add a lime sequestering product to slow down the formation of lime.

with water that is too soft (below 10°f French)

  • Use a product to increase the TH to 15°F French then adjust the pH of your pool (TH+ if the TH is very low, otherwise calcium hypochlorite)