Le chlore est le produit le plus couramment utilisé pour traiter l’eau des piscines et spas. C’est aussi le traitement le plus économique comparé au brome et au sel. Sa propriété désinfectante élimine tous les micro-organismes dans l’eau et c’est un algicide efficace. Vous hésitez dans le choix du traitement de votre piscine ou spa ? Lisez cet article pour tout savoir.
![Healthy and clear water. chlorine](/wp-content/uploads/2022/06/04-iPhone-ICO_preview-1080x675-1-1024x640.webp)
What is chlorine?
Le chlore est un élément chimique qui fait partie des halogènes comme le fluor et le brome. C’est à la fois un désinfectant et un oxydant dont le rôle est essentiel pour maintenir une eau saine et équilibrée. Comme le brome, il s’agit d’un désinfectant et un algicide préventif. Le taux de chlore varie en fonction du pH de la piscine. Si le pH est trop élevé (pH>8), le chlore devient inefficace.
It's the transformation of chlorine into chloramine (in contact with body pollutants) that creates this characteristic odor. In other words, it's possible to smell the quality of chlorine-treated water. If your pool or spa smells of chlorine, it's because the water is fairly polluted.
Chlorine in all its forms
Le chlore pour piscine est conditionné sous plusieurs formes : liquide, galet ou poudre. Le pouvoir désinfectant du chlore ne change pas selon le conditionnement, en revanche cela impacte la vitesse de dilution dans l’eau et par conséquent son efficacité dans le temps. Il est donc tout à fait possible d’utiliser, selon vos besoins et la problématique, plusieurs formes de chlore.
Chlorine in pebbles
Chlorine pebbles are placed either in your pool's skimmer or in a floating diffuser (for freestanding/above-ground pools). On contact with the water, the pebbles gradually dissolve. Their slow action helps maintain chlorine levels. This is the ideal form for regular maintenance of your pool or spa. Depending on the number of bathers and filtration time, chlorine pebbles should be added once or twice a week. There are also pebbles for shock chlorination (at the start of the season, or to quickly treat a water quality problem), which work very quickly.
Chlorine powder or shock treatment
Powder chlorine dissolves quickly in water and is fast-acting. It is often used as a shock treatment to treat green algae or when restarting your pool after winterizing.
Liquid chlorine
Liquid chlorine has the reputation of being a little more difficult to dose and handle. The pool surround must be protected to prevent discoloration (watch out for splashes), and bathers must be prevented from entering the pool for several hours after pouring the product into the water. Liquid chlorine is rarely used by private individuals (unless their pool is equipped with a dosing pump). It is more commonly used in public pools.
The different types of chlorine to disinfect your pool/spa
There are two commercially available types of chlorine for disinfecting your pool or spa water, stabilized chlorine and non-stabilized chlorine.
Unstalibized Chlorine
It has a high disinfectant power, but UV rays can significantly reduce its disinfectant power within a few hours. After 3 hours' exposure to the sun, 5% of unstabilized chlorine and 70% of stabilized chlorine remain in your pool. You can top this up with a stabilizer at the start of the season. This product is more commonly used by spa owners (who have a cover) and indoor pool owners.
Stabilized chlorine
As its name suggests, it contains a stabilizer, cyanuric acid, which protects it from UV rays. This is the form of chlorine most commonly used in swimming pools for its comfortable and complete use. Be careful, however, as the stabilizer (which must be between 30 and 75 mg/L) accumulates in the water and blocks the disinfectant action of chlorine. What's more, there's no way of lowering it except by draining part of the pool water. Stabilized chlorine must therefore be dosed with the utmost precision, and measured weekly.
Chlorine is a highly potent chemical and must be handled with care: gloves, masks and goggles (for liquid chlorine). Store out of reach of children and pets, in a dry, well-ventilated place.
How do you measure the chlorine level in your pool or spa?
Depending on the measurement tools used, they do not all analyze the same chlorine.
![diagram showing the different forms of chlorine. Only active chlorine, measured by the ORP ICO sensor, is responsible for disinfecting pool water. Chlorine strips measure all chlorines indiscriminately, and are therefore less effective.](https://ondilo.com/wp-content/uploads/2024/08/chlorine-measured-by-ORP-ICO-sensor-vs-strip-measurement.webp)
Total chlorine, Free chlorine, Active chlorine
First of all, you need to know that there are several types of chlorine: total chlorine, free chlorine, potential chlorine and active chlorine. When chlorine comes into contact with water, it is transformed into active chlorine and potential chlorine.
When chlorine turns into chloramine (also known as combined chlorine), on contact with organic matter (sweat, dead skin, etc.), or depending on water temperature and pH. Chloramines are responsible for the specific odor of swimming pools.
Not every chlorine molecule is responsible for or active in disinfection. Active chlorine is the only chlorine active in water disinfection. The more chloramines a water contains, the less active chlorine it contains.
Chlorine measurement tools
Because some chlorines are not involved in water disinfection (total chlorine, free chlorine and potential chlorine), make sure that the measuring system you choose analyzes free chlorine, as it is this measurement that gives you the right information on water health.
- Colorimetric strips are used to assess chlorine content (make sure you're measuring active chlorine). Many brands measure total or free chlorine. While this is a very economical solution, the results are highly subjective and not very accurate. Finally, it's important to read and scrupulously respect storage conditions and expiration dates, as humidity or heat can alter the performance of test strips.
- Connected photometers or water analyzers. Ces appareils de mesure donnent des chiffres digitaux beaucoup plus précis et fiables. Les appareils connectés, tels que ICO permettent de surveiller l’eau en mesurant notamment le chlore automatiquement 24/7.
![Illustration for comparison the ORP sensor in the ICO connected water analyzer measures the chlorine responsible for water disinfection. it's also more accurate than test strips.](https://ondilo.com/wp-content/uploads/2024/08/reliable-chlorine-measurement-with-ico-vs-test-strip.webp)
Advantages and inconvenience of chlorine treatment
The advantages of chlorine treatment for your pool or spa
Chlorine treatment offers many advantages. Firstly, it's a powerful algaecide and disinfectant that's easy to use. It's also the most economical product, compared with other water treatments such as salt and bromine. Finally, it's available everywhere (supermarkets, specialist stores, etc.).
The disadvantages of chlorine water treatment
The smell of chlorine, or more precisely chloramine, can be a real turn-off for some people. When incorrectly dosed, it can cause irritation to the eyes and mucous membranes, as well as discomfort to the skin. Secondly, chlorine is less UV-stable. If your pool is particularly exposed to the sun, it may be better to consider a salt treatment. Lastly, chlorine levels vary according to pH: this is a parameter that needs to be carefully and regularly monitored to maintain good water quality.
Key facts about chlorine water treatment
Water treatment for swimming pools and spas is undoubtedly the most classic of all treatments. Economical and practical, chlorine's effectiveness in disinfecting water is widely recognized. Nevertheless, it remains a chemical product that must be handled with great care to protect the health of bathers.