Principles of CO2 treatment
CO2 treatment
CO2 gas (carbon dioxide) exists naturally. It is naturally present in sparkling water, for example. More information on CO2 can be found in our FAQs. The Hydrokube CO2 softener injects CO2 proportionally into your water circuit. It then dissolves the limescale in the water, transforming it into water-soluble calcium bicarbonate. Calcium bicarbonate is used in food (E290) as an acidity regulator and stabilizer, and in medicine to regulate heart pressure. Next, we’ll explain the Hydrokube treatment principle in more detail. That’s why it’s important to explain what scaling is and how it occurs. It’s not easy to explain, but it makes a lot of sense when you consider that it’s all a question of balance between the ions present in the water.
Scaling
Scaling is the formation of calcium carbonate (and, to a lesser extent, magnesium carbonate). However, calcium carbonate, or limestone, (chemical formula CaCO3) can only form if certain conditions are met. Consequently, the reaction, visualized in the formula below, moves to the right (scaling) or stays to the left (dissolving limestone) depending on these conditions. 
To have scaling (limescale), you need:
- a sufficiently high concentration of both reagents: Ca2+ and HCO32- and
- low CO2 concentration.
Limestone is not dissolved in water (see chemical formula). As a result, these so-called hard waters tend to produce deposits, leading to the formation of crystals at the solid-liquid interface. Such water can cause scaling in homes, for example. Conversely, if the reagents Ca2+ and HCO32- are in low concentration in the water or the water is rich in CO2, the reaction shifts to the left and will tend to dissolve the limestone. The limestone is replaced by calcium bicarbonate.
CO2 prevents limescale formation
Hard tap water contains a lot of calcium ions (Ca2+). If you want to prevent the formation of limestone, CaCO3, or dissolve it. As explained in the previous paragraph, you need to act by increasing the CO2 concentration. The reaction moves to the left and will tend to dissolve the limestone. The hydrokube is based on this principle of CO2 injection. TheCalcium bicarbonate is unique in that it only exists dissolved in water! The balance is maintained by the CO2 mixed with the water. Calcium (and magnesium) are always present in water (see water hardness measurement). In reality, there is a concentration of CO2 that will guarantee total treatment of the limestone and thus balance the reaction. CO2 content influences pH. We can conclude that for a given mineralization, there is a pH value that corresponds to the target value for total limestone treatment. If the concentration of CO2 dissolved in the water is higher than this equilibrium concentration, the excess CO2 can dissolve the limestone, CaCO3. But it can also prevent its formation.
Conclusion
The CO2 injection system is based on this principle, which is fully consistent with water chemistry and the calco-carbonic reactions that take place in it. It is therefore logical that such a process should prevent the formation of scale in sanitary installations for both cold and hot water. The advantage of this treatment is that it’s environmentally friendly, economical and keeps tap water safe to drink.
