Too much cyanuric acid in the water?

09 March 2018

The function of cyanuric acid in the swimming pool

Cyanuric acid ends up in your pool water via regular chlorine tablets and chlorine granules.  This substance is added to these chlorine products to stabilise them. This stabilisation prevents the free chlorine from being decomposed by UV light.

At a high UV index, the sunlight decomposes 50% of the free chlorine per 45 min. Stabilisation is therefore absolutely required when using regular chlorine tablets or granules. These chlorine products are in fact less effective than inorganic chlorine products.

As long as the cyanuric acid concentration is less than 20 mg/l, there will not be any problem. Once a level of 70 mg/l is exceeded, cyanuric acid becomes problematic. Too high a concentration can, however, easily be solved. All you need to do is add fresh water to the pool (3 to 5% of the total volume).

The function of cyanuric acid in the swimming pool

Advantages and disadvantages of cyanuric acid

As already mentioned, the advantage of cyanuric acid is that it stabilises regular chlorine products. The free chlorine will decompose less rapidly under the influence of UV light, increasing the lifetime of these products.

However, cyanuric acid also makes the free chlorine less active, reducing its disinfecting effect. At a cyanuric acid concentration above 70 mg/l, the free chlorine will no longer disinfect at all. Extreme concentrations may even lead to green water!

Solution and tips for the pool owner

Solution and tips for the pool owner

Chlorine products containing cyanuric acid are not Vlarem II certified. Regular chlorine products may therefore not be used in public swimming pools, hotels, wellness centres, etc.

The use of these products is also not recommended for private swimming pools. With free chlorine that has poor disinfecting capacity, there is an increased risk of ear infection, although the risk is considered very small.

We can, of course, offer you an alternative, or better still, two alternatives. Instead of regular chlorine tablets or granulates, you could use the HTH granular chlorine. This product does not contain cyanuric acid, so none of the problems are present.

The second alternative is liquid chlorine or chlorine liquid. This product can only be collected at our physical shops, because it is not authorised for transport by regular courier service. The HTH granular chlorine, by contrast, can be delivered without any problem.

Do you have any further questions about cyanuric acid? Then do not hesitate to contact us! We will be glad to help you.