Strange noise in cavity wall?


Postby nmcl » Wed Sep 10, 2008 11:01 pm

Hi. In the past week or so we've noticed a strange hammering/pumping noise coming from an external wall in our downstairs toilet. It's fairly low volume, but there constantly. The wall seems to be the point where the gas and water come into the house and maybe the electrics as well (not really sure how to tell that one). At first we thought it was a water leak, but it's way too quick for that as far as I can tell, and there's no evidence of a leak around the wall inside or outside. (The nearest equivalent I can think of is that it sounds like a muffled jack-hammer.)

I turned off the central heating in case it was related to the gas or hot water, but that didn't make a difference. I turned off the electric and the sound was still there. If I turn off the water (the stop-cock is about 2 feet from where the noise seems to be coming) then the noise remains once again. The only thing that seems to make a difference is if we turn the water pressure up full: the noise level increases as the pressure increases.

The house is old (19th century) but this bit of the house is a 1970's extension. Is it possible that there's some meter in the wall that's gone into overdrive and is connected to the mains so that I can't switch it off? (Gas, electric and water meters are elsewhere, so I've no idea what else it could be measuring).

I don't want to go ripping up the wall on a whim, but it's starting to worry me that that's what we're going to have to do.

Any help and suggestions would be appreciated.
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Postby kbrownie » Thu Sep 11, 2008 12:14 pm

hi, i don't think this post really belongs in this section and the plumbing/heating section may be a better place for a better response.
Although it is an external wall is it a brick/block wall or a stud/timber frame wall, I can only assume as you state when water pressure is increased that the pipework is becoming more stressed, check the water pressure is around the 1.5 bar mark, if any higher needs to be reduced. If your pipe work is not correctly fixed, spaced and lagged it can create the pipes to creek.
Again try plumbing section better qualified knowledge available.
Regards
KB
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Postby kuzz » Thu Sep 11, 2008 4:25 pm

rodents?
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Postby nmcl » Thu Sep 11, 2008 6:38 pm

[quote="kbrownie"]hi, i don't think this post really belongs in this section and the plumbing/heating section may be a better place for a better response.
Although it is an external wall is it a brick/block wall or a stud/timber frame wall, I can only assume as you state when water pressure is increased that the pipework is becoming more stressed, check the water pressure is around the 1.5 bar mark, if any higher needs to be reduced. If your pipe work is not correctly fixed, spaced and lagged it can create the pipes to creek.
Again try plumbing section better qualified knowledge available.
Regards
KB[/quote]

Thanks, I'll try elsewhere. Not knowing what is causing the problem makes it difficult to know where to post ;-)
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Postby kbrownie » Fri Sep 12, 2008 11:44 am

Yes that's the best move, I doubt by what you have explained that it is an electrical fault or caused by electrical equipement and nor do I consider that rodents prime suspects, they can be noisey but the way you have explained the noise i'd disguard it.
KB
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Postby griffo » Tue Sep 23, 2008 5:15 pm

Its probably your Inlet Ball Valve in your Cystern for the toilet, replace it and I would put money on it that the nosie will go away.
Steve.
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Postby chris_on_tour2002 » Fri Sep 26, 2008 9:49 pm

highly unlikely this is an electrical problem. try the suggestion made by griffo and change the valve in your cistern - certainly sounds feasible as the noise is in your toilet.

if that fails then the sound is almost certainly water hammer - caused by too high a pressure on the incoming main. as you say that the noise lessens when you reduce the water pressure at the stop cock then i feel this is the most likely cause. shut off your stop cock completely then open it a quarter turn at a time until you get the desired pressure and the noise stops.

check that pipes are clipped and soundly fixed where accessible. a plumber can help with water hammer solutions if the problem persists.
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