cannot find incoming water question

Eric12 · Oct 28, 2021

Hello, yesterday I went to look at a small job, just an extra socket for a garage door. Bonding to gas is visible, where its fed from the CU in 10mm, but nothing to water. Long story short we couldnt find the incoming water anywhere despite looking in all usual places like under sink, under all the kitchen cupboards, under stairs, in the garage ect ect. Could not find anything atall even resembling incoming water so told the customer I need to test with meter (boiler disconnected) to verify its earthed ect. Thing is it might be plastic incoming, probably not, but might be. What would you do in situations like this ? Just interested. No response to my quote btw, customer probaly thinks im pulling her leg !

pc1966 · Oct 28, 2021

The danger here is probably mostly when on TN-C-S as if water is extraneous and not bonded, you might well find all of the neutral current in an open-PEN fault exiting via the CPC to a shower unit or (not so likely here) the power cable CPC to a gas boiler, neither of which could carry tens of amps for however long it takes the DNO to fix something.

Bonding gas and all water pipes at the boiler, and hot-cold tap feeds at any sinks, would achieve it provided the plumbing is not plastic in places. Which of course is not likely to stay that way after any repair work these days...

You might want to check with any neighbours to see if they know where their supply pipe is and the house/flat shares a similar design and construction?

Eric12 · Oct 28, 2021

pc1966 said:
The danger here is probably mostly when on TN-C-S as if water is extraneous and not bonded, you might well find all of the neutral current in an open-PEN fault exiting via the CPC to a shower unit or (not so likely here) the power cable CPC to a gas boiler, neither of which could carry tens of amps for however long it takes the DNO to fix something.

Bonding gas and all water pipes at the boiler, and hot-cold tap feeds at any sinks, would achieve it provided the plumbing is not plastic in places. Which of course is not likely to stay that way after any repair work these days...

You might want to check with any neighbours to see if they know where their supply pipe is and the house/flat shares a similar design and construction?

Not so much a danger on a TN-S, which it is. I could ram in a temp earth rod and IR test between that and a water pipe(s) in the house. Then if the water is extraneous like you say bond to boiler and check for plastic sections. She wont go for that thou. It does annoy me when this happens, builders have previously "revamped" the place and likely boarded over the water mains. That said ive seen some houses where main stopcock is outside in the pavement but at least the pipe is visible where it comes in !