Pool Stabilizer: Definitions and Advice

Vérifier son taux de stabilisant dans sa piscine

Combined with chlorine in stabilized chlorine products, pool stabilizer is your pool water’s best friend and worst nightmare at the same time. Find out more about the properties of pool stabilizer in our article.


The stabilizer or (iso)cyanuric acid (ACy) is a chemical compound whose role is to protect the chlorine against the UV rays of the sun. It guarantees a much longer life of the active chlorine in the water. Stabilizer is mainly used in stabilized chlorine (chlorine tabs, slow dissolution chlorine, etc).

This issue is that it is “bio-accumulative”. That means that, unlike chlorine, it does not evaporate, but it accumulates in your pool. This is why it is essential to monitor its stabilizer level using analysis strips.

Note: stabilizer concerns chlorine and salt treated pools.

What Is the Ideal Levels of Stabilizer?

The ideal levels of stabilizer is said to be between 20 and 50 ppm.

If the level of stabilizer in the water is too low (lower at 20 ppm), the chlorine in your pool will be almost completely gone in a few hours. In fact, according to studies, ultraviolet rays can reduce the power of chlorine by up to 90% in just 2 hours!

On the other hand, when the level of stabilizer exceeds 70 ppm per liter of water, there is an excess of product. An excess of stabilizer is not bad for your health, but it reduces the effectiveness of chlorine, making it ineffective. This generally creates a significant gap between the chlorine level in the water and the disinfection potential of the water (Redox Potential – ORP). The water is thus prone to bacteria/ algae development.

Signs of Over-Stabilized Water

The water is probably over-stabilized if you observe:

  • A correct or even high chlorine level while the water is cloudy or green;
  • A balanced pH and a high chlorine level, but a very low ORP.

To be sure, perform a strip test to measure the level of stabilizer in your water.

The Solution

The only effective way to get rid of stabilizer in your pool is to dilute the water. You will need to drain about 1/3 of the water from the pool and then refill it with fresh water.

If you have a bottom drain: cut the filtration for a few hours (one night for example) so that the stabilizer collects in the bottom of the pool then empty 1/3 of the water by the bottom drain.

How to Avoid Over-Stabilization?

  • All chlorines are not created equal! Prefer the use of 1st quality tabs or powders, the latter being much less dosed with stabilizer than entry-level chlorine.;
  • Replace at least a third of the water in your swimming pool each year. If your pool water is more than 3 years old, check the level of stabilizer when it comes out of winter. There is no point in starting a balance or disinfection if the stabilizer level is already very high.;
  • Use active oxygen powder* or unstabilized chlorine instead of stabilized shock chlorine.

*Iopool active oxygen powder only available in France

Find more information on stabilized chlorine and its benefits in our article.

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