'Foghorn' noise when cold tap switched on

[daffo]

Every time the cold water tap is switched on a 'foghorn' type hooting comes from the pipes. It only stops if you turn the cold water tap off then on again. This has been happening since we had a new cloakroom plumbed in in April. Anyone any idea why, & what to do about it ?

 

[Agile]

Possibly some pipework has not been properly clipped and is resonating under some flow conditions?

What does the installer of the cloakroom say?

Tony

 

[doitall]

Wc ballvalve is plastic, chuck it away and fit another

 

[daffo]

Installer was a relative just starting out in plumbing. Have told him about this site ! Thanks for replies.