Whistling/wheezing/screeching pipe noises when tap turned on

[Bourlet]

[FONT=arial, sans-serif]We have an intermittent issue with a noisy pipe in our kitchen/bathroom- when the tap is turned on there is a loud continuous squeaking/whistling/wheezing noise. When the tap is on, the noise seems to be coming from a pipe (connecting to the toilet I think) in the bathroom directly nextdoor to the kitchen. However the sound can be heard very audibly from the kitchen even with kitchen and bathroom door shut. There doesn't seem to be any difference whether it's hot or cold water, although sometimes the pressure of the water appears to be affected. Also worth mentioning- on a couple of occasions, we have heard the noise (verrrryy loudly) without the tap even being on..[/FONT]
[FONT=arial, sans-serif]As mentioned, it is intermittent so quite difficult to pin point. We have had a plumber and our building management over to have a look however on both occasions, the noise didn't happen (typically!) I did however take a video of it on my phone to show them (fearing that it wouldn't happen when they visited) but they still couldn't diagnose the problem. I've searched other forums and googled the problem to try and get to the bottom of it, 'water hammer' crops up alot but from the description of that i don't think that's what this is. If anyone has any suggestions as to what this problem could be, please please enlighten me! Thanks alot.[/FONT]
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[mountainman]

It's possibly water hammer but typically, unless the noise happens when your plumber is present it can be difficult to guess the problem.

 

[galaxy_plumbing]

could be stuck washer on valve or check if isolation valves are fully open but as already said, it never happens when plumber around so hard to tell

 

[Whyme]

Could be the mains stopcock jumper washer rattling around. this can happen when any outlet off the mains opens up ie toilet not just taps.Also it can sound like the QE2 sounding its horn all over the house..Worth a thought.