Calculate your water's Langelier index

Enter your analysis data and we will instantly show you the Langelier index, the Ryznar index and how your water will behave: whether it is corrosive, balanced or tends to form scale.

Indicative result, calculated using the Langelier (Carrier) method. For a diagnosis of your installation, measure continuously or contact us.

What is the Langelier index?

The Langelier index indicates whether water is scale-forming or aggressive (corrosive). It is based on the equilibrium between carbon dioxide, bicarbonates and carbonates, and depends on the water's pH, temperature, calcium concentration, alkalinity and total salinity.

It is a key parameter for preventing corrosion or scaling in distribution networks and in industrial and domestic installations:

• Index equal to 0: the water is balanced. It neither forms scale nor dissolves existing deposits.
• Negative index: the water is corrosive. It is undersaturated with calcium carbonate (CaCO₃) and tends to dissolve the layers that protect pipes and equipment.
• Positive index: the water is scale-forming. It is supersaturated with calcium carbonate and scale may form.

In Spain, Real Decreto 3/2023 (Royal Decree 3/2023 on drinking water), which replaced Real Decreto 140/2003, keeps the Langelier index among the indicator parameters of water quality. As a guide, it is recommended to be between −0.5 and +0.5. In swimming pools, the optimum value is between −0.3 and +0.3.

How to correct it

• Scale-forming water (positive index): reduce the pH or alkalinity.
• Corrosive water (negative index): increase the pH, alkalinity or calcium hardness.

With our pH, conductivity, temperature and hardness probes you can monitor the index continuously and receive alerts before problems arise. View the catalogue.