Vibrating cold pipe in down stair WC

[Colin68]

Hi All, (apologies if this has already been covered in advance)

After a customer visit last week, the poor guy has got a 'farting pipes' (as he describes it). The down stairs WC cold pipe vibrates when the WC is flushed and the cold tap open in the basin .. The kitchen sink (rather under it) has incoming supply with what looks like a 25mm (or more) blue poly, connected to a Gate valve stopcock, this go off to feed upstairs and the downstairs WC etc, cold pipe go under the floor (tiled) .. I have traced the vibration all the way back to under the sink (I think) .. the incoming pressure has been checked (via garden tap) and measures about 5.2 .. what's deal here? .. badly clipped pipes? .. vibrating gate vale? .. never seen this before in my travels .. it sometimes transfers (the noise) to the top floor WC too (three storey dwelling) .. any ideas from you seasoned pros ?

 

[warrington]

If it happens after flushing WC as you say, faulty ball valve.

 

[Colin68]

Happens when the basin tap is opened on its own .. no supply demand to WC

 

[AWheating]

probably problem with the tap. If your pressure measurement was dynamic (working) then it may be best to fit a pressure reducing valve as the taps and fixtures may not be designed to operate/coulld be tempremental at 5.2 bar.

 

[Colin68]

thanks .. I am convinced the pressure is too high at these outlets and suggested to the customer it could need reducing .. but could this effect the services on the top floor WC? .. or can the pressure reducer be set up and down (never fitted one before)

 

[AWheating]

1 bar = 10m

so if you reduce the mains pressure to a more normal 3 bar then you could still get 1bar of pressure 20m up.

how did you measure the pressure? did the outside tap have a check valve?

 

[Colin68]

I measure using the garden tap and attached a water pressure gauge to it and opened the tap fully

 

[PlumbBobBob]

that's standing pressure, you need also working pressure. you measure working by having kitchen tap on with gauge on garden tap also on.

 

[Colin68]

ok, will need to check 'working' pressure also. I also flushed the WC and nipped back the stopcock while the WC was filling and the vibration reduced significantly

 

[WaterTight]

well there's your answer them surely.

that was either coincidence or a PRV will sort it

could always be others factors at play too but first port of call would be prv i reckon.

or nip the stopcock back even more for a cheaper fix

 

[Colin68]

will suggest a PRV 1st .. more money in it for me then

 

[zzzjim]

'farting pipes' (as he describes it)

Is this called water hammer ?,
or am I showing my age !

 

[AWheating]

if the outside tap has a check valve then make sure the kitchen tap is running/fully open before turning the outside tap on otherwise the check valve will still cause you to get a standing pressure reading. It would be better to find another test point if a check is present tho.