Corrosive or encrusting water?
All water can be corrosive, fouling or balanced, regardless of whether it is potable. When it is corrosive, it affects the most easily oxidizable metals, such as galvanized steel or copper. Its tendency to corrode or to embed depends on the type and amount of inorganic compounds dissolved in it. One of the first characteristics that we must know about the water that we receive at home or in the company, is this trend.
We must not lose sight of the fact that we are not referring to a health issue, but to an issue of affecting the pipes and water treatment equipment.
There are five parameters that determine the trend of a water: pH, total hardness, total alkalinity, total dissolved solids, and temperature.
The pH measures the concentration of acids that dissociate when dissolved in water. It can have values between 0 and 14. A pH of 7 means neutrality. A pH less than 7 corresponds to acidic water, and a pH greater than 7 corresponds to alkaline water. The lower the pH, the more acidic the water, and therefore the more corrosive. And, vice versa, the higher the pH, the more encrusting the water.
Hardness is a measure of the concentration of dissolved calcium and magnesium in water. These cations tend to embed more than any other, so that, with greater hardness, the fouling tendency of a water increases.
Total alkalinity is a measure of the concentration of carbonates, bicarbonates, and hydroxides in water. All of these tend to scale, so water with a high total alkalinity tends to be fouling.
The total dissolved solids and the temperature increase the corrosive or encrusting tendency that gives the combination of the previous parameters (pH, hardness and alkalinity).
One of the most used indices to determine the corrosive or encrusting tendency of a water is the Langelier Saturation Index (ISL). When this has values between -0.5 and 0.5, the water is balanced (the best state of equilibrium occurs when the ISL is 0.0). When the ISL is greater than 0.5, the water is very fouling, and when the ISL is less than -0.5, it is very corrosive. In these last two cases, it is necessary to correct the tendency of the water. It is possible to do it in various ways (adding an acid or an alkali, softening, osmotizing, decalcalising ...)
The best is a balanced water, but what affects the treatment equipment the most is an encrusting water. This is so, because their internals (activated carbon, ion exchange resins, reverse osmosis membranes, quartz tubes from UV lamps, etc.) become encrusted and lose their ability to treat water.
When a softener is installed, it is common for the water to be corrosive. Therefore, before doing so, it is necessary that you go to a water technician to avoid this condition.
From all this, before anything else, it is necessary to determine the ISL of the water, to know if it has a tendency to corrode or embed, and to, if so, act accordingly.