Why does my current clamp meter show large current in gas pipe?

[Lister1987]

this can be very dangerous situation especially to other tradespeople like plumbers who may expose themselves.

Dirty dirty feckers ?

 

[Lucien Nunes]

I wouldn't say that current was high enough to imply there is a fault, it sounds more like ordinary CNE current finding parallel paths back to the substation via extraneous metal services as described by @Pretty Mouth above. The resistance of buried metallic services is in the same order of magnitude as that of the cables, so when they are all connected together, currents of the same order of magnitude can flow through them.

 

[Lister1987]

e5 did so videos on this phenomenon we know as Diverted Neutral Current;