Help with a plumbing problem, please.

Tringa

Tringa

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Dave
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Can anyone with a plumbing mind help me?

We are lucky enough to own two houses. We were last in the second house about six weeks ago and everything, plumbing-wise, was fine and no one else has been in the house since.

We arrived here last week and when one of the toilets is flushed there is a loud sound(imagine a low note from a brass instrument or a foghorn) as the cistern refills which continues until the cistern is full. The sound is constant – no hammering.

I took the cistern lid off and the sound does not appear to originate there. The inlet to the cistern vibrates a little but as I feel further down the water inlet pipe towards the floor the vibration is stronger.

If I turn the wash basin, which is in the same bathroom, cold tap on, even if only for a couple of seconds or so, and then off, the sound stops and does not re-start. Leaving the cold tap running does not stop the sound.

The sound happens only with this toilet – all of the other taps, showers or toilets work perfectly.

If I reduce the flow into the cistern via the isolation valve I can almost stop the noise happening but I have to just about close the valve completely.

I'm puzzled why this is happening now when six weeks ago it wasn't and no one has been in the house since then.


Can anyone suggest a cause and how this problem can be cured?

Thanks

Dave
 
I'd replace the valve in the cistern, or a least take it apart and see if anything, grit, swarf, etc has made its way in there. Sounds like there is some resonance going on and a length of pipe under the floor is vibrating against the floorboards because of some function of the valve. It could be happening because of something in the valve, something has shrunk/expanded such as floorboards due to temperature or some combination of factors. It could also be that the water pressure to the property has changed due to water mains repairs, etc.
 
We had the same thing a while back, when we flushed the toilet then came the noise which would stop if we turned a tap on. I noticed that the kitchen tap although turned off dribbled a bit when the noise occurred so I reasoned that it must be faulty and replaced it and that cured the noise.

I suppose we were lucky as it was relatively easy to see that the kitchen tap was faulty as it drippled when we heard the noise. I assume that the valve in the tap had gone and the noise was caused by water forcing its way through.

PS.
I've just had a thought. If your taps have isolators (I don't know the plumbing name...) in the pipes under them maybe turn them off one at a time and see if that helps pin the noise down.
 
Last edited:
Thanks all.

Dave
 
Was going to suggest water pressure as I’m sure you get high and low pressure ballcocks, quite how you check I don’t know sorry.
 
mj4456 said:
Was going to suggest water pressure as I’m sure you get high and low pressure ballcocks, quite how you check I don’t know sorry.
Click to expand...
They’re usually universal nowadays and you change the valve seat to adapt to high (mains) or low ( tank) pressure. Large size seat for low, small for high.

The noise is caused by water hammer as someone said previously. You can get rid of it by adjusting the water pressure; usually throttling the stopcock or isolation valve down a bit cures it.
 
We get a high pitched whistle if we use a cold tap and the cistern is filling.
Had it for twenty years so nothing serious, often wondered why though?
 
A length of pipe somewhere along the supply line is just the right (well, wrong!!!) length to set up a standing harmonic wave. This can be anything from a low hum to a banshee wail! We have a pair of old socks stuffed behind the rising main supply to the roof tank and they have damped the loud hum we get without the socks!
 
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