Diagnosing a waterhammer / "clunk" / pipe whirr?

[danb77]

Hi all,

I live in a small block of flats about 10 years old. Over the last year or so many of the flats have developed "clunk" sounds when taps are turned off and whirring when the water is running.

The mains water pipes run behind my bedroom wall, so I am trying to figure out the problem to get it fixed!

I suspected high water pressure, so I purchased a pressure gauge. However, this measures a static pressure of approx 2.3 bar, not an excessive level.

However, I did notice that when I measure the pressure, and run a tap, and then quickly turn the water off, the pressure leaps to over 5 bar! Could this be the cause of the clunks? Is there something stopping the water from releasing its "momentum" when a tap is turned, leading to an excess pressure and the noise? Or is this behaviour normal?

Also if anyone has any ideas what might start all the taps in a flat block clunking at once I'd be keen to hear them!

Thanks a lot,

Dan

 

[Newboy]

1) Change in water supply pressure

2) Partial closure of the stopcock(s)

3) Failed shock arrestor

4) Taps changed from screw-down to 1/4 turn

5) Modifications to pipework

6) Deadlegs

or something else!

 

[danb77]

Thanks Newboy! All good suggestions

1) Change in water supply pressure

I wondered this, but our pressure at 2.2 bar is relatively low.

2) Partial closure of the stopcock(s)

Not this, stopcock is fully open (though I wonder if it is fitted the wrong way round? The way it is fitted, the water main is arriving from above, which surprises me)

3) Failed shock arrestor

I don't think any of these were installed

4) Taps changed from screw-down to 1/4 turn

Taps are still screw down

5) Modifications to pipework

6) Deadlegs

I have a dead-leg, which I was just discussing here in another thread! //www.diynot.com/diy/threads/mystery-pipe-next-to-stopcock.422475/
Interesting.

or something else!

 

[Newboy]

If the stopcock is fitted backwards then there will be vibration as the headgear vibrates on the seat.

Check the flow direction on the body of the valve and see if it matches the actual flow direction

PS - not unusual to have mains supply pipework dropping down in flats

 

[danb77]

Thanks all. I'm going to ask the housing association who manage the block to get a plumber out. Suspect the pipes in the main riser are loose and so carrying the noise.

 

[Newboy]

Bear in mind that the possible cause apply to other flats not just your own - especially if taps have been changed.