Water descaling

You apparently do not know what the scope of maintenance is, do you?

A regeneration does not clean all parts of the system.

And honestly: not everyone has such a lax attitude as you - you should not assume that when you give such "tips".

But from a certain water hardness onwards, such a system is worth the money. Our water has 29.4 °dH. In our apartment building, however, there is only one such filter, which is absolutely useless.

When I see how the kettle has a layer of limescale after being used twice or the sink immediately has limescale stains, not to mention how the water pipes look, it would be worth an annual maintenance for me as well.

Apparently you don't know what the scope of a maintenance is, do you?

A regeneration does not clean all parts of the system.

And honestly: not everyone has such a lax attitude as you do – you shouldn't assume that when you give such "tips".

I didn’t know until recently that an annual maintenance is required. Nobody told me that when I bought it. They only said that the system would be checked “every few years” during heating maintenance.

Since the topic came up now, I took a closer look. For my system from BWT, annual maintenance costs of 130 - 160 € are to be expected.

However, there are descriptions on the internet on how to perform maintenance yourself. Below is a brief summary:
First, the system including connecting lines is visually inspected for defects (visual inspection). Then the salt tank is checked to see if the salt is clean and if there are any other contaminants in the tank. If yes, this tank is disinfected and the salt is replaced.
Afterwards, the water hardness at the outlet is measured. If everything is fine, the service interval is reset. Done. (I take no responsibility if someone does it that way and problems occur ;-))

I will try this personally after one year – but if you want to be on the safe side, you should of course call a service technician.

With, for example, Grünbeck systems, it’s a bit more... there is also a distinction between two services - one that should be done every x months and can be done by oneself (visual inspections) & once the "real" maintenance, which also replaces/cleans some filters.

Just to be clear again: What other types of water softening are there?

For use throughout the entire house? No effective ones!

For the kitchen sink, for example, you can use a reverse osmosis system, but the water is then almost fully desalinated.