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It is advisable to wait until the water temperature has risen above 15°C and remains stable before reopening your swimming pool.

This involves quickly raising the level of disinfectant in the water. It is done by adding fast-dissolving chlorine (such as powder) directly into the pool water. It is generally recommended as a remedial measure (if your water has turned green, for example) or during hot weather, or even after your pool has been used a lot. The recommended chlorine level in a swimming pool is between 1.5 and 3.0 mg/l and up to 3.5 mg/l in a spa.

In order to correctly measure out treatment products, you need to know the volume of your pool. HTH offers a simple calculation tool to determine the volume of your pool ➽ here

It is recommended to wait approximately 24 hours after a chlorine shock treatment. In all cases, check the chlorine content before allowing swimming. You can swim when the chlorine level is below 4 mg/l.

The filtration time for a swimming pool depends largely on the water temperature. A simple rule applies: Take the water temperature, divide the number by 2 and add 1 hour. Example: if the water is at 24°C = 24 / 2 = 12 + 1 hour = 13 hours. HTH offers an automatic calculator ➽ here

In order to measure out HTH products correctly, you need to know the volume of your pool. HTH offers a simple calculation tool to help you work out the volume of your pool ➽ click here

There are several reasons that contribute to this phenomenon.

• pH too high
• Insufficient amount of disinfectant
• Insufficient filtration
• Presence of limescale (hard water)
• Sur-stabilisation

Remember to monitor these various parameters in the water regularly.

If your pool water has turned green, it means that algae has developed. This is a sign of a lack of disinfectant, but not only that. You need to act quickly, but it is not necessary to empty the pool. See our advice on the subject of GREEN WATER ➽ here

Calcium hypochlorite (Ca(ClO)₂) is an non stabilised form of chlorine, meaning it does not contain any stabiliser, also known as cyanuric acid. Unlike “stabilised chlorine” used in many common treatments, it disinfects the water without any risk of over-stabilisation.

Over-stabilisation occurs when excessive amounts of stabiliser accumulate in the water. Since cyanuric acid does not evaporate, it builds up with every addition of stabilised chlorine. Although it protects chlorine from the sun’s UV rays, too much of it eventually reduces chlorine’s disinfecting effectiveness. Using calcium hypochlorite therefore helps reduce how often you need to drain your pool.