pH and Alkalinity: The Foundation of Healthy, Balanced Pool Water

January 13, 2026
by Mathieu Aubertin

When it comes to pool or spa maintenance, attention often focuses on disinfectants like chlorine or bromine. However, pH and alkalinity are the true foundations of balanced water. Without them, even the best products lose effectiveness.

Understanding their role not only helps maintain comfortable and safe water but also protects equipment and simplifies daily maintenance.

What is pH?

pH measures the acidity or alkalinity level of water on a scale from 0 to 14.

Low pH: acidic water
High pH: alkaline water
Ideal pH for a pool or spa: between 7.2 and 7.6

This range ensures bather comfort while maximizing disinfectant effectiveness.

Why a small pH variation has a big impact

pH operates on a logarithmic scale, meaning each unit change represents a major shift in water chemistry. Specifically, a difference of 1 pH point makes the water approximately 10 times more acidic or 10 times more alkaline.

For example:

Water at pH 6 is 10 times more acidic than water at pH 7
Water at pH 5 is 100 times more acidic than water at pH 7
Water at pH 8 is 10 times more alkaline than water at pH 7
Water at pH 9 is 100 times more alkaline

This is why a deviation that seems minimal on a test strip can have significant consequences for bather comfort, product effectiveness, and equipment longevity.

The effects of unbalanced pH

A pH outside the recommended range can lead to several problems:

Eye and skin irritation
Cloudy water
Equipment corrosion (pH too low)
Scale formation (pH too high)
Greatly reduced disinfectant effectiveness

👉 Even with a good dose of chlorine or bromine, an improper pH significantly reduces disinfection capacity.

Alkalinity: the pH stabilizer

Total alkalinity acts as a chemical buffer that prevents pH from fluctuating too quickly.

Ideal alkalinity: 80 to 120 ppm
Alkalinity too low: unstable pH, constant variations
Alkalinity too high: pH difficult to adjust

Alkalinity can be compared to a car's shock absorbers: without it, the pH goes up and down with the slightest change.

The link between pH, alkalinity, and chemicals

All products used in a pool or spa have a direct impact on pH, and sometimes on alkalinity.

Acidic products

Trichlorine chlorine
Muriatic acid
➡️ Tend to lower pH

Alkaline products

Calcium hypochlorite
Sodium carbonate
➡️ Tend to raise pH

This is why it is normal to have to adjust the pH depending on the products used, especially when the basic balance is not well established.

The advantage of pH-neutral products

Some products are designed to improve water quality without disturbing the chemical balance.

Example: monopersulfate (active oxygen)

pH very close to neutral
Hardly affects pH or alkalinity
Excellent oxidizing agent complementary to chlorine or bromine
Reduces organic load without causing imbalance

👉 pH-neutral products allow for:

fewer chemical corrections
more stable water
simpler and more predictable maintenance

Focus on balance rather than constant corrections

Effective maintenance is not about correcting pH every day, but about maintaining overall balance:

Well-adjusted alkalinity stabilizes pH
Stable pH makes disinfectants more effective
Well-chosen products limit variations

Result: more comfortable water, protected equipment, and fewer unnecessary added products.

Conclusion

pH and alkalinity are the pillars of healthy, stable, and comfortable pool or spa water. Even before increasing or decreasing disinfectant levels, it is essential to ensure that these two parameters are well balanced.

Understanding the logarithmic operation of pH and the impact of the products used helps avoid repeated imbalances, simplify maintenance, and fully enjoy clear and pleasant water throughout the season.