Have you checked if any of the siphons in the drains are being sucked dry? Under-pressure in the drain pipes (due to blocked vents or bad design) can suck the water out of the siphons essentially allowing the air from the sewer to vent directly into the room? Would typically occur when other apartments down stream flush water through the system.

Let’s cancel him. We can’t have dissenting opinions. Everyone must be assimilated by the socialist-borg.

Resistance is futile

You are right - second picture shows it’s connected to the water tap.

It’s not rocket science.

Low pressure will prevent proper circulation e.g. you will freeze your ass off.

You need to figure out where there is a connection you can hook the water hose up to?

Once connected the process is as follows:

1. Turn of furnace.
2. Open tap water
3. Open valve on heating system
4. Monitor pressure - don’t overfill it
5. Shut off valve
6. Shut off tap water
7. Turn on furnace.

A few details. Important you follow the order of opening tap water and heating valve as described or you might push water from the heating system into you tap water supply. Don’t contaminate it - so follow the order described.

Do not not overfill… you have a safety release valve which will vent over pressure (looks to be the blue valve on your picture). However … they are rarely used, so once they open? They might not fully close again. Which means they will keep leaking until replaced. So don’t push it.

Hot water expands. Once the cold water you filled into the system heats up? It will expand and increase pressure slightly. So don’t fill it to the max pressure. Once the water heats? It might trigger the safety valve.

In conclusion. Not rocket science. It’s something every homeowners should be able to do on a yearly basis.

Pressure gauge on the second photo shows 5+ bars?

Russia lost two ships to a converted jet ski. That’s probably a loss of more than 400 million dollars… one of us…