Pool water treatment: a complete guide to keeping your pool healthy all year round

Water treatment is one of the fundamental pillars of pool maintenance. Whether it is a private, communal or public pool, keeping the water clean, balanced and free of microorganisms is not only a matter of appearance, but also of health and safety.

Why is it so important to treat pool water?

Pool water, being outdoors, is continuously exposed to external agents: dust, leaves, insects, sweat, urine, sun cream, rain... Without proper treatment, the water can:

• Look cloudy and greenish.
• Encourage the growth of algae and bacteria.
• Give off unpleasant smells.
• Cause irritation to skin, eyes and mucous membranes.
• Damage the pool shell, the pump or the filtration system.

Objectives of water treatment

• Disinfection that is effective against bacteria, viruses and organic matter.
• Chemical balance to protect the equipment and the swimmers.
• Visual clarity and a feeling of cleanliness.
• Prevention to reduce product consumption in the long term.

Types of pool water treatments

1. Disinfection: the basis of a healthy pool

Chlorine (slow, fast, multi-action)

It is the most widely used disinfectant because of its effectiveness and low cost. Available in different formats:

• Slow chlorine: gradual release to maintain stable levels.
• Fast chlorine: ideal for shock treatments.
• Multi-action chlorine: includes algaecide and flocculant.

Advantages:
✔ Economical
✔ High effectiveness against pathogens
✔ Easy to apply

Bromine

Most commonly used in spas or indoor pools. Ideal for people who are sensitive to chlorine.

Advantages:
✔ Does not irritate mucous membranes or eyes
✔ Effective at high pH and at high temperatures
✔ Less odour than chlorine

Active oxygen

A chlorine-free, more natural alternative. Recommended for children and people with sensitive skin.

Advantages:
✔ Odourless
✔ Does not dry out the skin
✔ No harsh residues

Salt electrolysis

A system that generates chlorine from salt using a salt chlorinator.

Advantages:
✔ Less use of chemicals
✔ Automatic, continuous treatment
✔ More ecological and gentler on the skin

Ultraviolet (UV) light

Disinfects without adding products to the water. Increasingly popular in heavily used pools.

Advantages:
✔ No chemical residues
✔ Drastically reduces chlorine use
✔ High effectiveness against microorganisms

2. pH regulation: essential balance

An incorrect pH reduces the effectiveness of the disinfectant and can cause irritation or damage equipment. The ideal is to keep it between 7.2 and 7.4.

Specific products:

• pH+: raises the pH when it is too acidic.
• pH-: lowers the pH when it is too alkaline.
• Alkalinity increasers: stabilise the pH.
• Chlorine stabilisers: protect against degradation from UV rays.

3. Prevention and removal of algae

Algae are one of the most common threats, especially in uncovered pools during the summer.

• Maintenance algaecides: prevent their appearance with weekly treatments.
• Shock algaecides: to eliminate algae once they have appeared.

? Some products have a clarifying effect, improving the transparency of the water.

4. Flocculation and clarification

The smallest particles are not easily filtered. This is where the following come in:

• Liquid flocculants: bind particles together so they settle on the bottom and can be removed with the pool cleaner.
• Clarifiers: improve the filter's capacity by retaining suspended particles.

5. Anti-scale and prevention of build-up

In areas with hard water, anti-scale products are essential.

• They prevent limescale deposits on impellers, heat exchangers and walls.
• They extend the life of the equipment.

6. Seasonal treatments and winterising

Even if the pool is not used in winter, the water must be maintained.

• Winterising products: keep the water clear and algae-free during the winter.
• Prior cleaning: it is essential to leave the walls, floor and waterline clean before closing.

Essential accessories for water treatment

Having the right accessories makes maintenance easier:

• Chlorine, pH and salt test kits.
• Digital meters and photometers.
• Floating or automatic dosing units.
• Salt chlorinators and pH controllers.

✅ Automation reduces errors and saves time.

How to choose the right treatment

Factors to take into account:

• Type of pool: built, above-ground, covered or outdoor.
• Water volume: affects the dosage calculation.
• Users: children, people with allergies, etc.
• Location and climate: sunny areas require chlorine stabilisation.
• Budget: there is everything from affordable manual systems to automated solutions.