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The fight against lime scale – prevention and correct descaling

Question: What can I do to prevent calcification problems with DYNAJET machines?

Answered by our Expert:

Deposits in the pipelines occur when water with a high mineral content, such as magnesium and calcium, remains in hot pipes. So calcification problems only occur regionally, where "hard" water, for example from mountain springs, is used in DYNAJET hot water machines of the th and sh or Dynabox series.

Soft water is the term used when less than 1.5 millimoles of calcium carbonate are present per litre of water. This corresponds to less than 8.4 °dH (German hardness). 

Hard water is more than 2.5 millimoles of calcium carbonate per litre (more than 14 °dH).

You can find out the hardness of the water from your local water supplier. Alternatively, you can carry out an analysis of the water yourself or have it carried out by a laboratory.

DYNAJET prescribes a hardness degree of 3-25 °dH for high-pressure cleaners up to 350 bar, 3-20 °dH are permitted for 500-1200 bar and above 1,200 bar the maximum value is 15 °dH. These values can be found in the operating instructions of each DYNAJET machine in the chapter "Water quality requirements".

What can you do if you have very hard water that greatly exceeds the prescribed values?

1. Always cool down the burner:

Before switching off a hot water machine, always let the burners cool down with water flowing through them. To do this, switch off the burner after the cleaning work has been completed and pull the gun while the machine is running until the thermostat display shows you that the system is clearly cooling down to a water temperature of less than 50 °C. The water temperature must be below 50 °C before the machine can be cleaned.

2. Detect limescale in time:
To determine whether the high-pressure lines have calcified, detachthe gun and start the machine in cold condition with the burners switched off. Select a high engine speed. The pressure gauge will now show you the pressure loss of your pipe system in bar. If this pressure loss is more than 50 bar, it is time to decalcify the machine.

3. Have a calcification protection installed:
DYNAJET offers limescale protection devices that reduce the build-up of limescale within certain limits.


The galvanic element used here constantly releases small amounts of zinc ions. As a result, the lime does not flocculate but forms very small particles which do not adhere in the pipe system due to the flow. The system offers a noticeable improvement but no protection against extremely hard water.

4. Decalcify the burner spiral.
Lime mainly clog the burner spiral. If you have detected limescale in the system and the pressure loss in your machine has already risen well above 50 bar, the only thing that helps is to decalcify the system. Similar to descaling a coffee machine, the high-pressure cleaner is rinsed with a descaling agent (usually based on acetic or citric acid). This causes the limescale to dissolve. Your DYNAJET service partner will be happy to carry out this procedure for you as part of machine maintenance.
It is important that only the burner spiral is flushed and that the sensitive sensors of the machine do not come into contact with the descaling agent. Seals and non-ferrous metals do not like this sharp treatment at all.

Further links:
Service Information 120124 (available with DYNAJET Extranet login account only)
Ask DYNAJET a question yourself