REGULATIONS AND STANDARDS FOR PUBLIC POOLS

water treatment

paddling pool, footbath, spa and pool

Different standards govern the public swimming pool regulations. Below are some important reminders for optimum management of pool water quality. The water quality of swimming pools open to the public must imperatively comply with the standards required by the A.R.S.

Here are the regulations for public swimming pools, aquatic centers, semi-public swimming pools and open to the public:

Public swimming pool regulations

The pH of the water should be between 6.9 and 7.7 ppm.

The combined chlorine (chloramines) must be less than 0.6 ppm.

Pool water without stabiliser (isocyanuric acid) should have an active chlorine content between 0.4 and 1.4 ppm.

A pool water with stabilizer must have a free chlorine of at least 2.0 ppm.

Indoor swimming pools must have a trichloramine in the air level of less than 0.5 mg/m³.

The level of stabilizer (isocyanuric acid) present in the water must be less than 75 ppm.

The mandatory supply of new water is a minimum of 30 liters per day and per bather (recommended 50 liters / bather / day).

The pH of water for public swimming pools :

In public and collective swimming pools, the regulations indicate that the pH of the water must ideally be close to 7.2 and 7.4.

How to correctly measure the pH of water ?

The pH of water is measured using a photometer for self-monitoring and a continuous analysis device for online measurement and regulation.

A balanced pH determines the effectiveness of the disinfectant and the calcium-carbon balance essential for water treatment.

An automatic regulation of pH and chlorination is strongly recommended to optimize pH and disinfection.

See the automatic pH regulator

pH balance with the Taylor balance :

The Taylor balance represents the calcium-carbon balance of water.

The diagram below will give you the equilibrium pH directly from the TH (total hardness) and the TAC (alkalinity), this will allow you to deduce what is the tendency of your water.

The equilibrium pH will be aligned with the 2 points corresponding to the TAC value and the pH value that you have measured.

This can help you during your measurements and corrections of the various parameters.

How to interpret the Taylor scale ?

The Taylor's scale is an indicator, it does not have to be adhered to precisely. It is valid at a water temperature of 24°C.

1. Measure the TAC, TH and pH of the water.

2. Place a point corresponding to the measured TAC value on the right-hand scale.

3. Place a point corresponding to the measured TH value on the left-hand scale.

4. Draw a line from point TAC to point TH.

5. Read the equilibrium pH value at the point of intersection on the central scale.

If the pH you measured is lower than the equilibrium pH, the water has an aggressive tendency.

If the pH measured is higher than the equilibrium pH, the water has a tendency to scale.

The importance of TAC (Complete Alkalimetric Title)

What is the TAC ?

The TAC corresponds to the quantity of carbonates and bicarbonates present in the pool water.

The TAC measurement is expressed in °F or in ppm (1 °F = 10 ppm) and determines the buffering capacity of the water.

Checking the TAC is not regulated in public swimming pools but it is recommended to check it at least once a year.

Pond water with a TAC of less than 100 ppm (10°F) causes a strong variation in pH. To reassemble it, you must use a TAC booster based on bicarbonate and sodium carbonate.

Pond water with a TAC greater than 300 ppm (30°F) causes whitish deposits on the water line and difficulty correcting the pH. To lower it you must use an anti-limescale product or even hydrochloric acid if it is very high.

A correct TAC should be between 80 and 120 ppm (between 8 and 12°F).

Calculation of free active chlorine

Active free chlorine is calculated by comparing the pH value with that of Free chlorine (DPD1).

To facilitate and avoid reading errors in the calculation table, Ozonex has created an intelligent and connected automatic regulator that can take charge of two amperometric probes in order to display at time t the value in free/active chlorine but also that of chlorine total/combined (chloramines).

See the automatic regulator

The active chlorine content is determined from the measurement of the free chlorine and the pH using the following table (for a water at 25°C).

Example : at pH 7.4 for 1.6 mg/l of free chlorine, there is 0.90 mg/l of active chlorine.

Do not hesitate to start a measurement again if the value seems out of the ordinary.

Calculation of combined chlorine (chloramines)

Combined chlorine => Total chlorine – free chlorine (the rate not to be exceeded is 0.6 ppm).

Chloramines come from the reaction of free chlorine with organic matter brought in by swimmers (sweat, saliva, dead skin, etc.). It is a very volatile gas that gives off a very unpleasant smell of chlorine and gives this feeling of irritation to the eyes.

The presence of chloramines causes a feeling of irritation in the eyes and mucous membranes. In the longer term, chloramines can cause :

asthma attacks.

chronic coughs.

allergies.

bronchiolitis in babies.

conjunctivitis, etc...

How to Treat or Lower Chloramines ?

maintain a pH of the water between 7.2 and 7.4.

water renewal (creates additional operating costs).

respect the main rules of hygiene :

- take a soapy shower before bathing to rid the skin of sweat, cream residue, cleanse dead skin...

- remove make-up before bathing.

- Encourage children to go to the toilet before swimming.

Using an ozonator for disinfection considerably reduces the formation of chloramines and will avoid excessive water renewal (ozone has the power to destroy all organic matter: bacteria, viruses, etc...).

Ozonators for public swimming pools

Water recycling in public swimming pools

The time for water recycling in public swimming pools must imperatively be done according to the following A.R.S standards :

For a spa => 2 times the volume of water per hour.

For a paddling pool => 30 minutes minimum.

For a pool :

- with a depth less than or equal to 1.50 m => complete recycling in 1h30.

- with a depth greater than 1.50 m => complete recycling in 4 hours.

- diving pool or diving pit => complete recycling in 8h00.

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