The relationship between water hardness and pH value

How bacteria can develop in the whirlpool

Water hardness and pH are two very important parameters for successful water care in the whirlpool. Why is this so?

A whirlpool with 50 nozzles has approx. 100 m of piping with an inner surface of approx. 150 m². In the event of lime precipitation, hard rough limestone can settle on the 150 square meters. Bacteria use limestone as food. Fats and oils that get into the water through the skin easily stick to the rough surface and additionally serve the bacteria as food.

If several bacteria can settle and get enough food, they start with an accelerated cell division (proliferation). At 37° water temperature, bacteria can double their number every 20 minutes. One bacterium can become 1 billion bacteria in 10 hours.

As soon as several bacteria group together, they start to produce a kind of mucus. The so-called biofilm. This biofilm has many functions. The main function is to protect the bacteria from disinfectants. Another function is to filter nutrients from the water and provide them as food for the bacteria. Biofilms in the pipes should be avoided at all costs. Therefore the control of the water hardness and the pH-value is very important.

What is the relationship between water hardness and pH value?

When it rains, rainwater accumulates with the gas carbon dioxide from the air. Carbon dioxide is acidic and so the rainwater becomes slightly acidic. It has a pH value below 7.0.

If the rain falls on the earth and seeps away through a marble layer, the acidic water dissolves limestone and absorbs dissolved calcium ions. These calcium ions are in chemical equilibrium with the acidic water.

Water with many dissolved calcium ions is called hard water. There are different units with which one can indicate the water hardness. We use the unit "degree of German hardness".

  • From 7 - 10 °dH is ideal water for whirlpools
  • From 1 - 10 °dH is soft water
  • From 10 - 13 °dH is medium hard water
  • At 14 °dH water is considered hard

The conversion into °fH (degrees of French hardness) = 1 °dh x 1,78

The conversion into °eH (degrees of English hardness) = 1 °dh x 1,24

The water hardness of your water can be requested from your water supplier or measure it with our total hardness test kit.

How carbon dioxide influences the pH value >> 

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