Cold water main resonance

[Chrisscotty]

Evening all,

I have a traditional water system with a header tank in the loft. The cold rising main is vibrating slightly and causing a constant resonating noise, albeit quite a quiet one. The vibration stops when the internal stop cock is shut.

Any ideas on what may be causing this? I do have a long dead end pipe from a previous kitchen replacement...could this cause vibration?

Thanks in advance

 

[picasso]

Could be either the ballcock on the header tank or a toilet ballcock, isolate one thing at a time until you find it.

 

[Chrisscotty]

Thanks for the reply. I have already replaced the valve on the header tank and the toilet valve is gravity fed from the header tank so I'm assuming that it wouldn't be the cause?

 

[Galoka]

The tank ball valve might still be the source if the vibration,

Check that the pipe is secured properly, and yes, the log dead leg might be making it worse, so might be worth getting rid of it if you can

 

[Madrab]

Do you still get the resonance when the cistern is full and the valve's shut off? Or just when water is moving in the pipework?
Always get rid of any dead legs where possible, this can contaminate the cold water supply when the water in them goes stale. Due to the air that is invariably in them this can be compressed causing a pulsing in the pipework that can travel so could be the source of your vibration.

 

[Chrisscotty]

Yes I still get the resonance when the header tank valve is shut off.there is also no leak in the main as I have checked the meter. I have noticed that a reduction in pressure does help, although our pressure is not outrageously high at 3.5bar.

But the resonance does seem to pulse like it could be air in the dead leg as you say. Trouble is I can't see where the dead leg T's off the main. Would mean ripping up new carpet. Can you connect the dead leg back to the main forming a sort of loop in the main? Whilst not ideal would that help or would that be a no no!?

Thanks

Chris