Can I do maintenance on the descaling system myself?

Also 300 EUR (die richtige), the other one is actually just a visual inspection. You can't really book it like that.

Then I guess I'll have to take that on myself, although it still works (the specified hardness level of 7 is correct) and that's supposed to stay that way. Maybe you can watch and do part of it yourself next time.

Additional costs can be quite expensive. Ventilation and heat pumps theoretically also require maintenance; with the ventilation, we do most of it ourselves so far, with the heat pump, the technician has been there so often that I've saved myself that for now.

My plumber has now reported that I should rather have it done by the manufacturers (with me, besides descaling also the ventilation system from Vaillant), because it would be even more expensive with him. I could also maintain the ventilation myself, but then I would lose the warranty. I didn't actually want to do that in the first five years...
This will be expensive...

Ventilation: 283 EUR
WP: 260 EUR
Descaling: 301 EUR

yuck!

Our customer service comes once a year, which costs about 300 euros, they completely disassemble it, clean it and

Based on current experience in our company, I strongly advise having the system serviced according to the manufacturer’s instructions, otherwise the insurance will not cover damages; alternatively, take the system out of operation.
We had water damage (brine pump failed to pump out), costs around 10,000 euros, maintenance was 14 months ago and the requirement is every 6 months. Our system has now been taken offline (Grünberg DeltaP) because operating it is not worth it with such high maintenance costs.
Statement from a friendly independent plumber who knows the conditions: "If you call the factory customer service, they find a part every year that costs 600-800 euros to replace...". Of course everyone wants to earn money, but that sounds extreme.