I have a sealed central heating system with a water mains fed wall
mounted boiler in the garage with pressure relief valve and plumbed in
4bar expansion vessel. My house was recently extended with an added 6
radiators fitted to the system, and more recently, the diverter valve
failed and was replaced by local plumbers. We live in a relatively hard
After this work, there is periodically a relatively large bang coming
from the boiler area which causes a rattle along the pipes beneath the
floor. When the central heating is on this occurs maybe three or four
times in an evening, and is very common at the first fire of the boiler
in the morning.
Local plumbers have been out several times and best chance of
demonstrating the banging noise seemed to be by waiting for the central
heating to reach temperature and then turn down the thermostat swiftly
- bang! along the pipes when thermostat turned down.
The plumbers thought that I needed a larger expansion vessel (hence the
4 bar fitted one), but this made no difference at all. I then secured
all of the piping around the diverter vale with clamps to ensure no
loose pipes - but still we have bangs.
Any ideas that I can give to my plumber about what might be the problem