Common problems with domestic central heating systems often produce audible noises, from bubbling and rushing of water to squeaks and creaks in walls and beneath floorboards. Knowing what those noises signify means that you can often find and fix the problem before it gets worse.
Water Rushing Through Pipes
This sound is often not water rushing through the pipes, but rather air that has leaked into the system or gas caused by corrosion inside the pipework. You can bleed air or gas out of the system by loosening the valve on each of the radiators until water starts to drip out. Radiators keys for loosening the valves can be bought for less than £1 in any diy or hardware store. If this does not fix the problem, you can try to release air from any other venting points in the system. If the noise persists, call a qualified heating engineer as it could mean that there is a more serious fault.
Creaking In Floors and Walls
Creaking in the walls or floors that is directly related to the central heating (i.e. it only happens when the heating is switched on) is usually caused by the pipes expanding and rubbing against the joists, floorboards or studs that they are in contact with. It is rarely a sign of any major problem, but if you want to stop the noise the first things to try is to pack felt around the pipes where they come up through the floorboards. If this does not help, try to locate the noise as closely as you can and lift the floorboards in that area. Check that any notches the pipes pass through are wide enough, and widen if needed (don’t make them deeper as this may weaken the joist). You can also fit pipe clips to lift sagging pipes away from the timber.
If you can hear a humming sound, make sure that it is not coming from the pump in the boiler. This is often the cause and will probably need to be sorted out by a qualified heating engineer. An engineer will assess the problem and suggest a suitable solution (often as simple as fitting an anti-vibration bracket or turning down the speed of the pump slightly).
Banging pipes are usually a sign of overheating. Overheating can be caused by a faulty thermostat on the boiler. To check if your thermostat is working properly turn the boiler off, leaving the pump running to help cool the systems down. Once the system is cooled down, turn the boiler back on and turn the thermostat up. You should then hear a click to show that the thermostat has kicked in. If not, turn everything back off and call an engineer. If the thermostat is working, but the banging persists, you can try to stop it by cutting a piece of pipe out of the banging section and replacing it with flexible section of hose, connected to the original pipes with push fit fittings. As a last resort, remove the problem altogether and replace it with flexible plastic piping (making sure you choose piping which is suitable for heating systems).
Noises From the Boiler
The most common noise you will hear from a boiler, particularly older boilers, is a sound similar to a boiling kettle. This often signifies a build up of scale inside the heat exchanger. This can usually be fixed by adding a chemical descaler to the feed and expansion tank. Turn on your system to pump the solution through and then flush it with clean water. Finally refill the system.
Another cause of noises in a boiler is a low water flow. Having the correct water flow is particularly important in modern boilers. A heating engineer should be able to advise you about increasing water flow to a suitable level.