Shocks from running hot tap

[Zer0900]

Hi all,

this one is a first for me. Tenant says they are getting tingles when they run the water from hot tap in washand basin in downstairs bathroom. I haven't been to this callout as of yet, but just wondering what might be the cause for this. I am familiar with the houses in this area and I know that there is no earth rod inspection boxes visible. Most likely there is one but has been cemented over.

However even if a new one was driven and 10's ran to it from the CU, there still has to be an explanation as to why voltage would be present in running water at one sink. She says it doesn't happen at other sinks. Asked if she could see any green/yellow wires going to pipes in hot press, she says yes. Anyway. Will possibly have a look tomorrow. Any advice on where to begin the hunt? Thanks for reading.

 

[Richard Burns]

The last one I had like that was they had screwed through a cable below the tiled floor and then the shower started leaking and the wet floor became live but only gave shocks when at the earthed taps.
Check for above earth voltages on walls floors and pipes and areas of wet in the area of the sink.

 

[Zer0900]

Hi Richard,
Thanks for responding. I just left there after 4 hrs of torture. First, there was 80 volts at hot tap pipe going to the sink when measured between hot pipe and a neutral. 2nd, RCD test was failing to even start at 30mA and only tripped at 100mA. When tripped, it wouldn't re-engage. Changed that out. 3rd, after I changed it, it tripped about 40minutes later.

This turned out to be the fridge tripping it. It didn't before on the old RCD as it was shagged. Plugged in kettle there, no problems. So I try fridge on another socket with extension lead. Then it wouldn't trip....opened said socket with fridge unplugged. 80v across neutral and earth. But, when I plugged the fridge into it, this then jumped from 80v to 120v across neutral and earth, and did not trip the RCD.

So after belling out this cable and doing an IR test on it I find that this is the damaged cable that was causing my headache, but because it was in with another circuit naturally enough the same voltage was carried to 3 other sockets along the earth.

Once I disconnected the damaged cable from the CU the voltage dissapeared from the earth on the other 3 sockets.

Have to return tomorrow to run in a new circuit for the 2 now defunct sockets.

After this was done, I am happy to report that there is 0v on the pipe at the sink (but I ran a 2.5 earth to it from a socket the far side of the wall and bonded it anyway).

So I don't really know how the fault got to the sink. Maybe the cable is touching off a pipe wherever it is damaged and the voltage travelled through pipe from one point to another...?

If so though, why didn't the voltage carry across all earth's seeing as they all go back to the board. Also the fridge, it wouldn't trip on the damaged circuit that had 80v on the earth, bringing it to 120v with volt leakage from the fridge....I'm guessing there's an explanation for this. Anyway, thought I'd leave feedback. Just home now, but am glad it's sorted. Thanks for reading and if anyone can give explanations for any of the above please do so. Cheers.

 

[Marvo]

One of my worst ever faults was a shower giving tingling shocks. It was a 'favour' job that was 4 days work and unpaid.

Shocks from Bath tap - https://www.electriciansforums.co.uk/threads/shocks-from-bath-tap.70467/#post-688922

Good luck.

 

[Zer0900]

Holy ---- Marvo. That is just outright crazy. Never in a million years would've thought of that. Kudos to you for figuring it out! Unpaid to, to add salt, argggh.