Descale the water boiler - you have to pay attention

Descaling the water boiler is either a specialist thing - or you can try it yourself. How to proceed, what you should not forget and what you must pay attention to is explained here.

Basic procedure

Freeing the heating elements of the boiler from limescale occurs with the help of acid. Thus, the lime components which are precipitated on heating the water and form rock-like (dolomite) deposits can be removed. Other methods do not work.

Not all boilers allow for easy removal of the heating elements. Quite simply, it is usually with small sub-table devices. They almost always have a lid. For some large models, only the specialist can remove the heating elements.


Provide adequate lighting before starting work and have protective clothing suitable for handling acid. This includes:

  • rubber gloves
  • if possible safety goggles
  • long-sleeved, insensitive work clothes

Before working on the boiler, it must be disconnected from the mains. Under no circumstances may a boiler be opened while it is still powered! It must also be removed, the lines are secured, and then then tested again against neutral and protective conductor.

If you do not feel safe, have an electrician show you exactly how to proceed. Do not risk anything!

After that you have to shut off the water. There must no more hot water flow out of the water pipes.


Drain the water, clean the inside of the boiler of lime and check for damage. After pulling out the heating rod and the heating element can be cleaned and descaled. Use only recommended descaling agents (citric acid, formic acid) and follow the instructions for use carefully. Do not overdose!


After everything has been cleaned, the boiler can be reassembled, if the individual parts are not damaged (deformed or rusted heating elements, defective sacrificial anode, cracks or damages in the boiler).

Thoroughly rinse the boiler over cold water inlet and hot water outlet (connecting). All you have to do is turn on the faucet. Then the power can be reconnected, and then the fuse can be reactivated.

Tips & Tricks

Never connect an unfilled boiler to the mains! The heating elements can burn off in a few seconds.

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