Cold water pipe banging

[steveharr]

I have a problem where when I turn off my cold water taps in the bathroom (the only taps installed at the moment) the pipe bangs loudly and most of the noise seems to be coming right back from the water meter in the kitchen, but I can't be sure. The taps are new (1/4 turn type) and so is some of the pipe work.

I had a similar problem before which turned out to be the stopcock not open fully in another house. This house has two stopcocks one before the meter and one after. I twiddled both stopcocks and the noise reduced for the first time but returned again in fully glory.

Can anyone suggest anything?

 

[steveharr]

The taps are fed directly from cold supply, not via tank in attic

 

[kevplumb]

its called water hammer you can get a gizmo from plumbers merchants that allegedly stops it never used one so cant say only time i had a problem used a 15x15x28t and bit of copper with stop end the air in the pipe acts as a cushion

app a foot worked for me straght after incomer to house

 

[steveharr]

if my pipe run is vertical from meter do I need to T off and go around a bend to vertical to maintain an air cushion?

Anyone got any other ideas? PLease

 

[steveharr]

Please Help

 

[kevplumb]

if the run is vertical then yes you need to tee and get the pipe vertical otherwise it fills with water and defeats the object of the exercise
if you consider you have mains water at say two bar then you suddenly stop it bang roughly what airbags are for in cars if you think about it

 

[TexMex]

Water hammer is caused by the fast flowing water column, being abruptly stopped. You probably have 15mm pipe supplying your upstairs, replacing it with 22mm will cure the problem.

(The larger bore of the pipe means that the actual speed of the water in the column, is significantly slower).

 

[kevplumb]

nice one tex never thought of that flowrate combi etc etc