One approach to eliminate limescale is adding chemicals to water in order to prevent minerals from crystallizing. An alternative approach to this is that rather than forming a hard mass of crystals on the surface of pipes and appliances, the minerals form into small crystals in the water which are easily washed away by the flow. This is the basic principle of the Wave Limescale Eliminator protection against limescale.
When dissolved in water, these minerals are in the form of ions. These are atoms or small molecules that have an electric charge, either positive (cations) or negative (anions). The most commonly occurring ions are:
These positive and negative ions can combine to form crystals—e.g. calcium carbonate, also known as limescale —that attach to pipes and hot water appliances.
Because mineral ions have electrical charges, they can be manipulated by an electric field. The Wave Limescale Eliminator uses a specially designed electric field to help ions form crystals in water rather than on pipes. This electric field rapidly changes direction (it is an AC field) from upstream to downstream. Positive ions are moved one way, negative ions are moved the other. The field then changes direction along with the directions the ions move.
Figure 1: The AC field rapidly moves the ions in opposite directions
Moving the positive and negative ions that are initially dissolved in the water (Figure 2a) in opposite directions means they are much more likely to come into contact with each other, stick together and form clusters (Figure 2b). Clusters are loose collections of ions, each of which is surrounded by a thin layer of water molecules. The Limescale Eliminator signal is not continuous, but turns off and on at random intervals. This “jiggles” the clustered ions, helping them form more regular arrangements (Figure 2c), which helps them crystallize.
Figure 2: Formation of clusters and crystals
At this point, the ions are still dissolved in water (each ion has a layer of water around it). However, if this water is heated it cannot hold onto all the ions, as it becomes supersaturated and wants to get rid of ions by forming crystals. The clusters are the easiest way for this to happen, so the ions expel the water surrounding them and form tiny crystals in the water (Figure 2d).
Seed crystals and the prevention of scaling on pipes
How does the existence of these tiny crystals prevent limescale from building on the surface of household pipes? Crystals need a starting point to form, also called a nucleation site. If there is nothing else, the side of the pipes will serve as a starting point, and crystals will form on the pipe. However, crystals would rather form on an existing crystal. An illustration of this can be seen in Figure 3, which shows a simple children’s experiment. On the left, a string is dangled into water which has sugar dissolved into it. The best starting point for crystal formation is the string, so crystals have formed along the length of the string. On the right, a small sugar crystal is tied to the string before it is placed in the sugar water. Since crystals prefer to form on the existing sugar crystal, the existing crystal grows rather than new crystals forming along the string.
Figure 3: Crystals require a nucleation point, and will form along the surface of the string (left) if nothing else is present. However, they prefer to form on an existing crystal. The image on the right shows a seed crystal growing rather than new crystals.
We can now see how the formation of even a few “seed” crystals can prevent the formation of limescale on pipes. Without treatment (Figure 4), when water is heated, the only starting point for crystallization is the surface of pipes. As more ions begin to crystallize, they form on the existing crystals, and the scale on the surface of the pipe grows.
Figure 4: Scale forming on the surface of a pipe
With the Limescale Eliminator (Figure 5), the signal causes the ions to form into clusters, which water is heated become small crystals in the water . Now, when any further crystallization takes place, it does so by the growth of these crystals rather than by the formation of new crystals on the surface of the pipe. We see that by forming seed crystals, we prevent crystal formation anywhere else. These crystals are about 10 microns in size, i.e. one hundredth of a millimeter, and so are easily washed out by household water flow.
Figure 5: Crystals forming in suspension in the presence of HydroCare signal