For problems relating to sealed systems, seek the services of a professional heating engineer
A number of different things may cause noise problems with a heating system.
This is a sign that air has got into the system.
This can be released by bleeding air from the radiators.
but remember to turn the heating off first
Now, armed with a rag beneath, use a radiator key to slacken the air bleed valve which is sited at one end towards the top of the radiator. There will be a hissing sound as the air comes out. As soon as water begins to flow, close the valve again and wipe away any water.
Take care not to get scalded – the water may be pretty hot.
The heating can then be switched back on.
Some systems have an automatic air release valve fitted. This usually has a small red top which should be slack to enable the air to escape.
Radiators should not need frequent ‘bleeding’.
If they do, air is getting in and this should be sorted out by a professional heating installer.
The pump which sends the water around the system may be set too fast. In this case , try turning it down to a lower setting. Pumps can also cause this noise in the pipework through vibration of the pipes. This can be eliminated by mounting the pump on special brackets which absorb the vibration rather than transferring it to the pipes. Finally, the problem can arise where undersized pipes have been installed.
Check this out with a heating engineer.
Knocks and creaking
Everywhere that pipes pass through other materials like floor joists or walls, there is a possibility that they will rub when they expand or contract unless enough space has been left. If you can identify where the noise comes from, investigate the pipework in the area to see where it is rubbing. Rubbing against floor joists where the notch out is too narrow to allow a little movement, is a common cause. This can easily be widened by cutting an extra slither away from one side with a saw and chiselling away the waste.
Take care not to damage the pipe and do not deepen the notch as this weakens the joist.
You can also pack a bit of fibreglass insulation around them to cushion the rubbing. This packing can also help where pipes come up through floorboards.
Sometimes pipes running beneath the floorboards have not been supported properly.
If you find pipework which has a lot of free movement - for example where they run parallel to the joists - they will need to be secured.
Fit a small batten, screwed between the joists, and use pipe clips to retain the pipes.
This may be caused by sludge and scale inside the boiler which results in some areas heating up more than others. The result is usually intermittent banging caused by pockets of steam. The same sludge build up can also restrict the flow of water which will result in noisiness. Air in the boiler may also cause noises.
With any of these, it is recommended that you seek the services of a professional heating engineer.
There may be a lack of water. Check the feed and expansion tank. If it is not topping up when the ball valve is opened, there may be a frozen pipe, air lock, or the mains water may have been switched off.