why do you get green stain on brass stop cock

[helptavner]

our stop cock has a bit of a green stain on it, cant see any leaks!

previously was leaking from the gland / and we have a new tap fitted so the tap will have got wet in the past few months..

whats caues this please...

 

[Charnwood]

It’s probably verdigris.

green or bluish patina formed on copper, brass, or bronze surfaces exposed to the atmosphere for long periods of time, consisting principally of basic copper sulfate.

The stopcock could have got wet due to condensation, not a leak.

Copper tube is normally coated in a grease which helps to stop this occurring in the short term.

 

[helptavner]

helpfull as ever
thanks!!

 

[Charnwood]

One tries one's best.