Hi Christian,

In . net,
Christian McArdle wrote:
It's definitely hydraulic, not electrical.

I wasn't suggesting that the noise was coming from the electrical
equipment, just that it is the source.

Ah, OK. Bit hasty there.

It is quite common for some piece of electrical equipment to come in
contact with the water pipe and resonate it. You are likely to get
either 50Hz, 100Hz or harmonics thereof. It can be intermittent as
the equipment touches or otherwise as things move or expand with
temperature etc.

Bugger, I'll have to shut my computers down to find out.

OK, turning off the water at the stop-tap didn't shut it up. I removed the
pipe boxing from around it hoping there'd be something obvious but there
wasn't. I ran all the taps till the flow stopped [near as dammit, the
stop-tap's duff]. Still making a din, which didn't alter when I turned it
back on. If I could figure out why it suddenly started I'd be happier.
Ain't life like that?

So now, time to shutdown the computers.
Will report back.

--
Gill
got a headache now