Water balance

The pool water chemistry explained.

Langelier formula

To restore the water balance, you can use the formula of the saturation index below:




SI = pH + TF + CF + AF - TDSF

pH: pH value

TF: Temperature related factor

CF: Calcium hardness related factor (CH)

AF: Total alkalinity related factor (TA)

TDSF: Total Dissolved Solids related factor (TDS or total mineralization)



Saturation index

The water is in balance if the saturation index is between -0.5 and 0.5.


The below table illustrates the parameters factors that you will need to calculate your saturation index.


Tabel of parameters factors (water balance)

Temperature CTemperature factorCalcium ppmCalcium factorAlkalinity ppmAlkalinity factorMineralization (TDS) ppmTDS factor


The influence of pH level on the water.

pH is the total measurement of acidity in the water. The pH scale measures between 0 – 14 where pH 7 is considered neutral. If the waters pH indicates above 7, the water is considered basic. If the water pH indicates below 7, the water is considered acidic. To match with human pH, and for the best chlorine disinfection, it is recommended to keep the water pH at 7.4.

When the pH is low, it will give aggressive water that will damage the mechanical components of the pool and it will cause damage to the pool liner. Thus, it is good idea during the winter time, when also the temperature is low (5-10 degrees), to increase the pH level to protect the water from being corrosive.

Low pH will also irritate the eyes and mucus membranes.

If the pH is higher than normal, it will give poorer chlorine disinfection, can cause scaling properties, the water will be milky, and it will cause skin irritation.

You can adjust the pH levels according to the desired levels with Norlex PH Plus and Norlex PH Minus, depending on the circumstances.

You can adjust the pH levels according to the desired levels with Norlex PH Plus and Norlex PH Minus, depending on the circumstances.



What is calcium hardness? 

Calcium hardness is the amount of dissolved calcium that is present in the water.

The pH level is the most important parameter for balance, though, pool water requires certain amount of calcium to prevent corrosive water conditions. Ideal calcium hardness depends on multiple factors. E.g. the higher the temperature of the water, the more calcium deposit there will be, but if the pH value is low, it will regulate the scaling. The ideal calcium hardness range depends on the pH value and the temperature.

In lower temperatures (winter time), too low level of calcium content (soft water) in your swimming pool will cause the water to be corrosive and it will dissolve calcium and other minerals from pool surfaces and pool metal components. Therefore, it is advised to increase the pH level of the water to protect the equipment. Contrary, too high level of calcium in the pool water (hard water) will cause the water to be muddled and it will deposit calcium carbonate scale on pools surfaces and pools equipment, especially warmer surfaces, but not if the temperature is low and pH value is low.

It is important to measure the calcium hardness regularly to protect your swimming pool and its equipment from corrosion.


How does the alkalinity affect the pH?

Alkalinity of the pool is very important factor in the balance (Langelier), as it prevents the pH from sudden changes. It helps to stabilize the pH balance in your pool within normal ranges. To keep the pH level at balance the alkalinity level must stay above 80 ppm. The average swimming pool should have the alkalinity reading between 80- 120 ppm.

Low alkalinity will cause rapid changes in pH, and it will cause problems like: metal corrosion, chlorine deficiency, staining and scaling of the pool, itchy skin and burning eyes and nose.

Too high alkalinity will cause the pH to be much higher than the normal range. Cloudy pool water, reduced circulation, clogged filter and coarse surfaces, itchy skin, burning eyes and nose are good indicators that the alkalinity of the water is too high.

If the Alkalinity of your pool water is too low, you can adjust the alkalinity of the pool water with Norlex Alka Up.

If the alkalinity of the water is too high, to reduce it, simply add any acid. 



Any questions about water balance?

Get in touch