ᐅ Gas boiler ... How to refill water correctly? What is the proper sequence?

Created on: 1 Dec 2025 18:32
C
Curiosius
C
Curiosius
1 Dec 2025 18:32
Good evening,
I often hear on construction sites about how to refill a gas boiler with water...
This is how I did it, following the instructions of a plumber:
- Turn off the heating system or pump
- Set all radiators to level 5
- Wait about 30 minutes
- Connect the hose, filling it with water beforehand
- Open the valves on the boiler
- Slowly and carefully open the tap, watch the gauge, do not exceed the green zone
- Close everything again, disconnect the hose, and done

Is that correct?
curiosius
N
Nauer
1 Dec 2025 22:15
Hi Curiosius,

The approach is correct. However, I would question a few minor details. Setting the radiator to position 5 is not necessarily required, as long as you keep the heating off during filling. More important is to make sure you fully bleed the hose before connecting it to the boiler. Otherwise, you might end up with air in the system, which is rather suboptimal.
C
Curiosius
1 Dec 2025 22:32
Hi Nauer,
please also respond in the other thread, I want to implement this.