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Discuss Humming pipes in a combi boiler system, bleeding not helping. in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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wooding

Hi,

I've been having an annoying problem of humming pipes in a house. I've outlined the details below, I've had a plumber round who suggested they couldn't help without hearing the noise, however it isn't constant and mainly comes at night so this is proving impossible. Any advice would be greatly appreciated as I'm pretty much at a loss.

Combi boiler system in a house. Gloworm betacom2 24

Humming sound coming from pipes. Starts as an intermittent hum then builds to a solid tone that gets very loud, then fades off. Repeats.

The sound is loudest and seems to come from the wall by the bedroom door. The boiler is in the kitchen downstairs the only pipes I can imagine being in or near the wall are heating as the bathroom is further away. The boiler doesn't make the sound only the wall.

It's been coming and going for weeks, it mainly makes noise at night but also it happens in the evening and during the day sometimes.

It makes the noise when the heating is on and when it's off.

I've tried bleeding the radiators and adjusting the mains water pressure (I wasn't sure if it was the water or heating at first) but seeing where the sound comes from I'm guessing it's the heating.

The radiators in the upstairs bathroom and the airing cupboard both seem to gather a lot of air, I've been bleeding them every week and each time the airing cupboard radiator has had air in it. I'm guessing there's a leak or air getting into the system?

The boiler pressure cold was originally at 1.5. I've bled the radiators and topped the pressure up before, didn't have any effect. I think the pressure is down to about 1.3 now as I've been bleeding the airing cupboard and bathroom radiator.

There are 3 radiators I can't bleed, the downstairs hall, the bedroom and the spare room. The valves are worn and rounded and keys just slip on them. Although they all seem to be hot at the top so I don't know if they're ok anyway.

Other possible factors which probably have nothing to do with it, Toilet refills slowly from a very thin spurting valve, sink hot tap seems to leak around the base slightly, kitchen sink tap drips continuously.

Can anyone point me in the right direction?
 
Next time it makes the humming sound, go to a radiator with a thermostatic valve fitted. Turn that radiator off, then go one by one until you find the one that stops the sound. You will have a thermostatic radiator valve fitted the wrong way round.
 
Thanks very much for the reply, that's not a suggestion I've heard.
I will give it a try, it might take some time as the humming comes and goes pretty quick.

When you say the wrong way round do you mean it would need removing, turning 180 and replacing? or that it's on the wrong side of the radiator (the side water exits rather than enters)?

Just a note, the humming isn't coming from a wall near a radiator, the radiators are all on opposite walls quite fair from where the humming comes from. I don't know if that would make a difference?

I shall definitely be trying this anyway. Thanks again!
 
if you've a combi system then probably not got a water tank in the roof. Have had cases of humming/vibration due to slight ripples in tank moving the ballvalve slightly and causing noise as the flow is interrupted. Could be toilet cistern. When you hear the noise try turning on a mains tap or flush the toilet. If it stops it's mains noise. If it only happens when heating running it could be the TRV but normally the noise comes from the radiator.
 
Thanks for the reply.

I'm still testing the TRV method, I've been systematically adjusting them when I hear the noise, but it hasn't made a difference yet.

There is no water tank no. Unfortunately I've tried turning the taps and flushing the toilet and it has no effect.

That's what I'm finding so strange that it happens when the heating is on and when it isn't on (To be clear the boiler is on, I mean it happens whether the central heating is on and when it's off).

I'm also confused about the regular build up of air in one of the radiators, I thought combi boilers where a closed system which vented any air in the system?

And yes the sound seems to come from an upstairs wall which has pipes near it (and I think underneath) but not a radiator near it. The sound doesn't come directly from the boiler or a radiator.

Thanks for the advice.
 
1. dripping tap can cause problems with combi boilers , get dripping tap fixed, 2. ball valve in wc slight let by could cause noise , replace ball valve, If noise happens even when boiler is off then more than likely not boiler, if system seems to collect a lot of air, problem may not be Air could be corrosion in your system, get system cleaned and a inhibitor put in system.
Other than that your house is haunted !! does it hum a particular tune, have you thought about singing along with it ??
 
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