Hello, I joined this forum as it looks like a helpful place. So our boiler is at high pressure all the time, whether the heating is on it not (3bar). Hearing works fine and bleeding the radiators hasn't helped. It also starts to make a loud noise during the night. Never does it in the daytime. If I turn the mains water off, it stops. What could this be? Could someone also identify the flathead screw/valve on the pipes to the left on the picture as well and whether it should be set that way or not?
Thanks in advance
Thanks in advance