How do you lower the combined chlorine rate?



The combined chlorine rate is linked to disinfection using chlorin


The combined chlorine rate is linked to disinfection using chlorine. During the disinfection process, the chlorine will "combine" with bacteria, nitrogenous content, and organic compounds in order to destroy them. So it is normal to measure its presence in pools treated with chlorine.

However, when its rate is high, the combined chlorine will cause eye and skin irritations, and will be the reason for the "bad chlorine odour " coming from the pool.

Therefore, it is important to keep this rate as low as possible.

In order to reduce this rate to the maximum extent, the simplest method is to identify the source of the bacteria, algae and other compounds:

Filter descaling

Regardless of what water is in the pool, it will contain limestone. This will mainly become deposited in the filter and will enable algae, bacteria and fats to build up in it. Consequently, not only is the water in the pool subject to less efficient filtering, but the chlorine will also be consumed in the filter in order to destroy these substances. The outcome of this will be a high combined chlorine rate at the filter outlet which will be put directly into the pool.

By using the Acti Filter Cleaner product for cleaning filters, all of the scale deposits and fats will be eliminated. Thus, thanks to a purified filter, the water will be better filtered, and there will be no more pointless chlorine consumption. Due to this, the combined chlorine input into the pool will be greatly reduced.


The water balance enables a stable pH to be maintained, and therefore enables a constant level of chlorine activity. If the water is not balanced, the pH level will go up and down like a yoyo and the effectiveness of the chlorine will be greatly reduced, thereby facilitating a high combined chlorine rate.

By balancing the water in the pool, the chlorine will act more rapidly and will limit the combined chlorine content.


According to its disinfection process, 3 chlorine particles are required to finalise the combined chlorine formation/destruction stages. If the active chlorine content is too low, the disinfection will remain stuck at the combined chlorine formation stage and will not be able to destroy the substances.

The simplest method is to increase the active chlorine content (by adding chlorine or a one-off drop in the pH) in order to finalise the disinfection process.

To do this, use a photometer to precisely measure the free chlorine and total chlorine values, and then use the analysis software (which can be downloaded for free from this Website) and follow these treatment recommendations.

the Presence of phosphates (pollution)

If, in spite of all these precautions, the combined chlorine rate regularly remains high; this may be due to pollution caused by phosphates.

Phosphates are one of the food sources for algae and bacteria, and they will therefore facilitate their development in a water tank. The greater their numbers, the greater the chlorine demand will be. It is therefore of the utmost importance to limit the presence of phosphates in water by using the Acti Anti Phosphate product.

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