Treatment of a swimming pool with chlorine: principle and process


Chlorine is well known to homeowners since it is the most frequently used product to treat swimming pool water. Let’s find out what its exact role is, its main advantages, in what forms it is marketed, how to use it and what is the ideal chlorine level in a swimming pool.

Chlorine, a popular swimming pool disinfectant

The use of this Chemical product is almost essential to benefit from an irreproachable bathing water. It eliminates:

  • The mushrooms,
  • Bacteria,
  • The seaweeds.

Thus, chlorine is very useful so that young and old can enjoy a clean water and crystal clear. If this is the most commonly used swimming pool treatment, it is because it has the following advantages:

  • Effective due to its high algicidal (against algae) and antibacterial (against bacteria) power,
  • Easy to find, it is marketed by pool specialists, specialist retailers and supermarkets,
  • Affordable price, it is indeed much cheaper than bromine,
  • Easy to use,
  • Offered in different forms, namely in powder, in pebbles and in liquid form.

For information, powdered or pebbled chlorine costs on average 35 € per 5 kg jar, and between 55 and 60 € per 20-liter container (liquid chlorine).

Is chlorine harmful to swimmers?

Some people are reluctant to use chlorine because they suspect it can give their pool water a very unpleasant odor. Yet this chemical is odorless.

On the other hand, this very unpleasant specific odor for which he is accused is due to the transformation of chlorine into chloramines as soon as it comes into contact with ammonia or organic matter such as cosmetics, dander, sweat, saliva, but also the urine of bathers … (yes, some people are indelicate …) .

The pH and temperature of the water also affect the appearance of chloramines in a swimming pool. For example, the chlorine becomes totally ineffective with too high pH.

Chloramines, in addition to giving off a strong chlorine odor, irritate the eyes and skin of swimming pool users since they are toxic. They can also irritate the throat and nasal passages, even in occasional bathers in a chlorine-treated pool.

No risk irritation or allergy is not to be feared when the level of chloramines does not exceed 0.3 mg / m3 of water.

Regarding his handling, it implies some precautions to avoid inhaling, ingesting or getting in the eyes because it is especially in its solid form that chlorine is irritating to the mucous membranes, eyes and skin. It is therefore recommended to wear goggles and a protective mask as well as gloves whenever you have to handle chlorine. And since two precautions are better than one, we do the same if we have to use chlorine in its liquid form.

It makes good sense to store it in a lockable room, very good ventilated, dry, and which children should never have access to. It should always be stored in its original packaging, and empty chlorine cans or bottles should be discarded immediately as indicated on the labels. Finally, chlorine is never transferred into a container other than the one strictly intended for this chemical.

How to use chlorine to treat your swimming pool?

The mode of use depends on the form of chlorine, namely:

  • In powder (shock chlorine), to be poured directly into the swimming pool water. Its dissolution is very rapid. This is the form recommended for a shock treatment in a swimming pool that has become impracticable where the water is very dirty or very green, or quite simply when restarting after wintering.
  • In pebbles, perfect format to maintain an ideal chlorine level, to be placed in a floating diffuser or in the skimmers, once or twice a week depending on the length of time the pool is used and the number of swimmers. It is by far the most marketed form due to its ease of use and dosage. Its dissolution is slow.
  • Form liquid (rather reserved for public swimming pools, liquid chlorine is difficult to dose and its handling requires certain precautions.

It should also be noted that there is two types of chlorine.

  • Stabilized chlorine UV resistant because it contains a stabilizer. It is odorless, does not modify the pH of the water. You have to be precise about its dosage because if the chlorine dissolves quickly, this is not the case with the stabilizer it contains. Too high a dose, the latter ends up accumulating in the swimming pool water, making the chlorine ineffective. It is therefore necessary to ensure that the level of stabilizer is always less than 60 mg / liter of swimming pool water.
  • Unstabilized chlorine which must be supplemented with a stabilizer because it loses its effectiveness fairly quickly due to its propensity to degrade under the effect of ultraviolet rays. It is ultimately little used by pool owners.

Treating a swimming pool with chlorine: the right dosage

To measure the chlorine level in the swimming pool, we use chlorine-tests. It is strips which also analyze the pH level. The box of 50 units costs around ten euros at most. Some chlorine tests are marketed as lozenges, the DPD1 being the most effective lozenges. The box of 250 costs on average 15 €.

Finally, there is a more sophisticated way but also more expensive to measure the chlorine level, namely the device electronic tester the price of which varies according to the models from 50 to more than 300 €. But it is also the most reliable way which gives a result of high precision since we can thus measure the pH, the total chlorine level but also that of all its components, such as active chlorine, combined chlorine, stabilizer, etc.

Whatever process is used, this does not change the dosage of chlorine which must be observed. For optimal treatment, it is important that the dosage corresponds to the type of chlorine, namely:

  • Stabilized chlorine:
    • 0.4 and 1.4 mg / l: active chlorine,
    • 0.6 mg per liter at most: combined chlorine,
    • Between 7.2 and 7.4 for the pH.
  • Unstabilized chlorine:
    • At least 2 mg / l: active chlorine,
    • 0.6 mg per liter at most: combined chlorine,
    • Between 7.2 and 7.5 for the pH,
    • 25 mg / l: stabilizer (must never exceed 60 mg / l).

Each assay requires vigilance so that everyone can enjoy the swimming in all serenity. Some people prefer to make it easier for themselves. They opt for a chlorine regulator. It’s about a metering pump which only works with liquid chlorine. It is not necessary to intervene manually, the device regulating the rate in real time. A metering pump costs at least € 200.