ᐅ What type of water do you use in your underfloor heating system?

Hello everyone,
the neighbors in our semi-detached house have a different heating contractor, which is why I noticed the following difference:
Our heating technician used regular tap water to fill the underfloor heating system, while the neighbor’s technician used so-called osmosis water, which was treated with a kind of desalination system before filling.
What type of water do you use? Would you ask your heating contractor to change it again? Or is it generally not a concern if you live in an area where tap water is relatively low in limescale, for example?
Thank you very much for your input, and best regards
Anna

Of course, fully demineralized water should be used in the system. If untreated tap water is used, you can expect deposits, discoloration, and even rust in the system over time.

So, you mean water exchange? He will have to do it in the summer when the heating is off, right?

Well, you can also turn them off during the winter for that hour. It’s not a big deal.