Drinking water is heated and stored in hot-water boilers which are generally connected to the central heating system.  Or in a calorifier where  an electrical coil  is used to produce the heat. These boilers tend to scale up very greatly if the water is hard, primarily if the temperature is high accordingly. Frequently, such boilers also start to rust after a few years and this is why stainless steel boilers are used to a greater extent today.
Merus clears the scale in the boilers if used properly and this scale is then flushed out with the water. Existing rust deposits are partially dissolved and converted. At  boilers heated electrically might occure the problem of less efficiency, if the coil gives a strong electrical field. These electrical heating systems may emit fields, which impair the