Our boiler pressure was at zero a few days ago so we bled the radiators, which made no difference, and then loosened a valve with a screwdriver to let some pressure back in. This worked, however the valve wouldn't fully tighten again so I'm not sure if it's even properly closed. The pressure has stayed above 3 Bar since and there has been a constant gush of water from the overflow pipe outside. Every now again the boiler will make some very loud noises, almost like a drill. The pressure is also massively affected by the washing machine when it's running - pressure needle jumps all over the place and more loud drilling noises.