Which heating pipes are used nowadays?

Keep an eye on the material mix, mixing installation can go wrong.

Because the steel pipes are practically indestructible. And please be careful with the cross-section of the new pipes.

Is it an old gravity heating system or is there a circulation pump working in the system?

Yes, but doesn't it make sense to just replace it, especially since it can be relatively easily partially renewed? I thought I was doing the house a favor.

The heating system has a pump.

If composite pipes, then pay attention to what temperature they can withstand and how and with what they need to be processed if you want to do it yourself. Google Tece system. What kind of boiler do you have, a thermostat, cast iron or steel heating boiler. What supply temperature is being used?

They are simple copper pipes and it is a steel heating boiler. And no, I didn’t want to do that myself, at least not completely. I do trust myself with quite a bit, I also think I am handy. But so far I have stayed away from the heating system. However, I thought I could try to educate myself a bit.

The flow temperature is, I believe, a maximum of 70 or 75 degrees. It is automatically adjusted according to the outside temperature.
It is a house with 3 residential units. (Basement, ground floor, attic). In the basement and ground floor I could renew all the pipes step by step, whenever I want to plaster a room, I also want to wall up the niches and at the same time renew part of the piping. I hope to have all the radiator niches walled up by the end of next year.