I live on the 14th floor of a 30 story apartment building and so far, I’ve been bleeding my radiators myself.
This usually worked and after bleeding I had a fully functioning radiator, 100% filled with water.
However, last time I tried bleeding, it would only fill up to 25% of its volume, it’s like there’s no pressure in the circuit.
Am I doing something wrong?
That depends entirely on how the system is set up. I would only ever consider increasing the amount of water in the system if I was absolutely certain that my apartment was on a completely separate and closed circuit than the other apartments. You should contact the janitor or whatever it’s called.