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Things That Go Bump in The Night – Central Heating

Skill Level: Intermediate


You’d be surprised how many people live with noisy central heating. It is something many of us just put up with – fearing that it may result in having to replace the whole system. After all, apart from the noise (and actually you get used to it after a while), everything else seems to be working ok! At best it sounds as if there is something broken and needs replacing!................but that may not be the case. In many instances the answer to the noise problem is a lot simpler. It may be a knocking noise (somewhere?) the pumps making a funny clatter; perhaps there’s a sound like flushing or draining water rumbling? The pipes vibrate and are humming, or strange noises are coming from the boiler itself. We shall try and cover a few of these symptoms; identify the causes, and come up with some quick fixes

Pipes expand

As you can imagine; pipes expand and contract as they are heated, and as they cool down. Much of our central heating pipe work is located under floors and will be seated in grooves cut out of the floorboard joists. If the pipes are gripped tightly by the recessed joist, are touching other pipes, or are wedged against a wall, then this can result in creaking and rattling sounds. When pipes are situated up against a wall the sound will be transmitted through the wall, and into other areas of the house. It can be hard to know exactly from where the noise is originating. Pipes can also produce an irritating humming noise on occasions, sometimes as a result of being too small for the amount of water they are carrying ( hopefully this not the case)

Lagging pipes – Soundproofing

The first thing to try is lagging around the heating pipes where they come up through the floor. This can be done with either felt lagging or the foam sleeved type pipe lagging. This is sometimes enough to cure the rattling

Noises from under the Floorboards

When you have a rough idea where the noise is coming from you will need to lift the floorboards in that area and investigate further. Have a look at the pipes at the points where they cross the joists; they will be seated in cut-out recesses to accommodate the pipe (s) Are they wedged in tightly, with no room for movement during expansion? If this is the case, the best thing to do is gently, and carefully, cut the recess a little wider using a tenon saw and wood chisel. When you have done this, wrap a piece of felt lagging around and under the pipe; and between pipes where there is more than one in the recess. Don’t cut the recess any deeper, it’s not necessary and will only weaken the joist.

Pipe Clips and Other Supports

When pipes run in the same direction as the joists, unless they are supported at intervals, they will sag and rattle around. The best thing to do here is to nail a few wooden noggins between the joists, and attach plastic pipe clips to hold the pipe (s) firm

A Buzzing Sound Coming from the Pump

There can be a number of reasons for the central heating pump humming, or buzzing.
  • It could be that the pump speed is set too high.
  • It could be that fitting anti vibration pump brackets will cure the problem.

Loud Rattling Noise from the Pump

Combined with inefficient radiator temperature, this could be due to insufficient water in the system. Check the level in the cistern and if it is low make sure that the ball cock is working correctly

Noisy Boilers.

Over time, corrosion and scale can build up on the inside of the boiler causing localised hot spots which can pop and bang as a result of steam generation. Where you suspect this to be the case then add some non-acidic de-scaler and cleanser to the feed tank.

A boiler can make strange noises if the water flow is insufficient; with wall mounted, light weight boilers, the rate of water flow is particularly important, and this can be an issue. Where unsure; consult a professional.

Another common problem (and cause of noise) with heating systems is air entrapment. The quick solution is to simply bleed the radiators and any other vent points you may have; this will usually help. If the problem persists then call an expert; sooner rather than later, before it gets any worse


Tools you will need:

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