Softening system – protection against limescale build-up

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Viessmann softening systems, type VS 19D and VS 42D

Hard water can lead to permanent deposits. These not only affect the effort required for cleaning, but can also damage water pipes, connected components and household appliances that contain or use water. A water softening system reduces the hardness of the drinking water, which protects against calcification. This way, it helps to extend operational reliability and service life and at the same time increase convenience – and not only during regular cleaning. The Viessmann Vitoset range of accessories includes innovative drinking water softening systems for use in detached houses and apartment buildings, small commercial businesses and the catering trade.     

What is hard water?

The hardness of drinking water is caused by the lime it contains and the calcium and magnesium ions dissolved within it. The higher the proportion of these, the harder the water. A major influence on water hardness is the soil composition of the groundwater or spring water from which the drinking water is obtained. Water becomes hard when it comes into contact with limestone such as chalk or marble. You can find out more about the hardness of your drinking water from your local water supply utility. 

There are three different hardness ranges

Water hardness is expressed as the content of calcium carbonate in millimoles per litre (mmol/l). This value allows a distinction to be made between three hardness ranges, as the following table shows:

Hardness range

Calcium carbonate concentration (mmol/l)


German degrees of hardness (°dH)


Hard water

≥2.5 mmol/l

≥14  °dH

Medium hard water

≥1.5 < 2.5 mmol/l

≥8.4 < 14  °dH

Soft water

<1.5 mmol/l          

<8.4  °dH

What are the benefits of a softening system?

Hard water does have advantages. One is that it contains more minerals than soft water. In the long term, however, it causes limescale deposits to form in components containing or using water, and in household appliances. In addition to reducing service life, these deposits also reduce the heat transfer of heating rods and coils in washing machines and kettles, for example, leading to increased energy demand. Water softening definitely contributes to greater energy efficiency. In addition, water with a very high lime content makes it difficult to clean taps and fittings and increases consumption of detergents and cleaning agents, while also reducing their cleaning performance. The taste of hot drinks is also negatively affected. If the lime content is too high, water softening is definitely advisable.

Take advantage of these benefits of a softening system

  • Efficient protection against scale build-up inside DHW cylinders and pipework
  • Energy savings and extended service life of household appliances
  • Maximum shine in the bathroom due to significant reduction in limescale deposits
  • Supple skin and silky hair thanks to soft water
  • Soft laundry, gentle on fabric
  • Reduced consumption of detergent and cleaning agents

Viessmann drinking water softening systems are certified to DVGW.

How does a softening system work?

A water softening system from Viessmann works according to the reliable ion exchange process. With this method, the water flows through a resin charged with sodium ions. In the exchange process, it releases calcium and magnesium ions and absorbs sodium ions. In this way, the system produces fully softened drinking water. The blending valve included in the standard delivery is used to set the required soft water hardness easily. When the ion exchange resin becomes saturated, it needs to be recharged with sodium ions. However, the innovative control system of the Viessmann VS 19D and VS 42D softening systems ensures that only spent resin is regenerated. This leads to savings for salt and regeneration water. 

Bathroom with cleaning facilitated by a drinking water softening system.

Finding the right softening system

If you want to soften your water, it is important to choose the right system. The following table illustrates which Viessmann softening system is suitable depending on the water hardness and the number of people in the household (with recommended softening to 6  °dH):

  

12 °dH

15 °dH

18 °dH

21 °dH

24 °dH

27 °dH

30 °dH

33 °dH

36 °dH

1 to 3 occupants

VS 19D

VS 19D

VS 19D

VS 19D

VS 42D

VS 42D

VS 42D

VS 42D

VS 42D

4 to 6 occupants

VS 19D

VS 19D

VS 42D

VS 42D

VS 42D

VS 42D

VS 42D

    

7 to 9 occupants

VS 42D

VS 42D

VS 42D

VS 42D

VS 42D