Swimming Pool Water Analysis

The pH is a fundamental parameter for the chemical balance of the pool water. Keeping it within the range of 7.2 to 7.4 is crucial because:

• It ensures the effectiveness of chlorine: If the pH is outside this range, chlorine loses its disinfecting power.
• It avoids skin and eye irritations: An incorrect pH can cause discomfort to swimmers.
• Prevents scaling or corrosion: A high pH favors the accumulation of salts, while a low pH can corrode metal elements in the pool.
• Improves water quality: A stable pH reduces turbidity and improves water clarity

• Sampling point: 20 cm deep and 30 cm from the wall, away from water inlets. We recommend in the middle of the pool.
• Time: Preferably at the same time of day, avoiding periods of maximum use.
• Container: Use clean containers rinsed with pool water.

To choose the right system, you should consider:

The accuracy you need:

For basic maintenance, analytical strips may be sufficient.

If you are looking for more accuracy, a digital meter or photometer is the best choice.

Speed of measurement:

Manual strips and kits offer quick results in seconds or minutes. Photometers and digital meters require a little more time, but offer greater reliability.

Frequency of analysis:

If you test your water frequently, a fast, easy-to-use system will be key. If you need precise analysis, you might opt for photometers.

The choice of the measurement system for the analysis of your pool water depends not so much on the type of disinfection you use (chlorine, bromine, saline, active oxygen, etc.), but on the level of precision and speed you need in the measurement.

All measurement systems are compatible with any type of treatment, but there are differences in terms of reliability, ease of use and cost.

• Test strips: 10-30€ for 50-100 strips.
• Kits: 30-100€ for basic kits.
• Digital meters: 50-500€ per individual device (pH, ORP, etc.).
• Photometers: 200-1000€ depending on complexity and parameters measured

• Occasional home use: 1-2 times per week, strips or liquid kits are sufficient. We recommend measuring the salt level every month.
• Intensive or commercial use: Daily or several times a day, photometers or digital meters are more appropriate.
• Public pools: According to local regulations, usually several times a day with high precision equipment.

• Test strips: Accuracy of ±10-20%, suitable for quick controls.
• Cases: Accuracy of ±5-10%, require more skill but are more accurate than strips.
• Digital meters: Accuracy ±1-3%, excellent for specific parameters such as pH or ORP.
• Photometers: Accuracy of ±2-5%, ideal for professional measurements or public pools.

• pH: Measures the acidity or alkalinity of the water. The ideal range is between 7.2 and 7.612.
• Free chlorine: This is the active disinfectant in the water. The optimum level is usually between 1 and 1.5 ppm (parts per million)
• Total chlorine: Includes both free and combined chlorine Alkalinity: Helps stabilize pH. Recommended range is 80 to 150 ppm
• Calcium hardness: Measures the concentration of calcium minerals. The ideal level is between 200 and 400 ppm
• Cyanuric acid (stabilizer): Helps keep chlorine stable under sunlight.
• ORP (Oxidation Reduction Potential): Measures the disinfectant capacity of the water.

Also, depending on the type of pool and treatment, you may need to measure:

• Salinity: For pools with saline chlorination.
• Phosphates: Can contribute to algae growth.
• Metals: Such as copper or iron, which can cause staining.

If the pH is too high (>7.8):

• Chlorine effectiveness is reduced, allowing bacteria and algae to grow.
• May cause eye and skin irritation. Increases water turbidity.
• Encourages the formation of calcium scale in pipes and equipment.
• Can clog filters and reduce the efficiency of the recirculation system.

If the pH is too low (

• Increases the aggressiveness of the water, which can cause corrosion in pipes, pumps and metal fittings.
• May cause irritation to the eyes, skin and mucous membranes of bathers.
• Makes chlorine more aggressive and consumed faster, generating strong odors and affecting the chemical stability of the water.

The pH has a direct relationship to the effectiveness of chlorine in water.

How pH influences the disinfecting power of chlorine:

• At pH 7.2, about 66% of the chlorine is in its most effective form (hypochlorous acid, HOCl).
• At pH 7.6, only 42% of the chlorine is active.
• At pH 8.0, chlorine efficiency drops to 25%.

If the pH is high (>7.8):

• More hypochlorite (ClO-) is formed, which is less effective than hypochlorous acid (HOCl).
• This means that, even if there is enough chlorine in the water, its disinfection capacity will be lower.

If the pH is low (

• The amount of hypochlorous acid (HOCl) increases, making chlorine more effective.
• However, a very low pH can cause the chlorine to be used up quickly and cause irritation to bathers.

To measure the salinity of the water in a pool with salt electrolysis, it is recommended to use digital conductivity and TDS (total dissolved solids) meters, since salt influences the electrical conductivity of the water.

Methods for measuring salinity:

Digital EC/TDS (Electrical Conductivity/Total Dissolved Solids) meters

• They allow accurate and fast measurement.
• Some models such as HI 98302 and HI 98312 offer combined measurement of TDS, conductivity and temperature.

Salinity test strips

• Less accurate method, but useful for quick control.