Shower shocks !!!

[RDC1979]

Hi guys,

in need of some advice, this is my first time on here so be gentle..!

I had a client call me to ask to look at a shower in one of his properties as the tennants are complaining of little shocks from the shower taps??
i immediately told them to isolate until i can have a look.

Once i arrived i did a quick visual and noticed 10mm bonding on water and gas, i verified those connections with a test. The readings on the water were a little high 0.20
The pipes behind the shower in the cupboard were cross bonded and I had similar readings.

Before I isolated I took a live Zs on the circuits and they were all ok, proving earth path all ok on them and all but 2 circuits were RCD protected.
I then took a Zs at DB and was happy with that


I then took a Ze reading which was satisfactory and whilst at the board i did an IR test on the non RCD protected circuits and it came back all ok.
I also tested the RCD and that was disconnecting in the required time.

I then stumbled across a circuit that was still connected and live but no longer being used, this was hidden in the same cupboard, i believe for an old immersion.

I disconnected the circuit from the board and went back to test verify, no voltage on L-N, but If I tested across L or N and the pipes I was getting 30v?

My first question is,
Is this just induced voltage? could these pipes be run in parallel and picking something up that being stood in a wet shower tray you can feel? I'm guessing not?

But If I went across the screws on the face plate and the pipes I also get 30v again?

so I did an IR test again on this circuit and all was ok.

So my second question is,

If there was an intermittent earth fault and the pipes were somehow picking up a current from something and bonding was not sufficient, surely they would feel this throughout the house not just in the shower?

And my 3rd question is

My plan was to run another 10mm cable direct to the MET from the shower pipes to resolve this, and if I get the required 0.05 what else should I try?

I am due to go back this weekend to continue my investigation but I'm starting to wish I never took this one on? I have been recently responding to faults to gain experience in fault finding and I will definitely be taking an experienced fault finder back with me just thought I would ask.

Thanks in advance guys !

 

[davesparks]

What's wrong with a 0.20 ohm reading on the main bond?

Have you carried out insulation resistance testing on all circuits in the property? If you have did you find a low reading somewhere?

Adding a 10mm bond to the shower pipework won't fix anything it will just mask the actual fault.

 

[telectrix]

take an analogue meter. then see if you still have 30V. also with power on to the shower, measure L-N and L-E. if they are identical then the's no voltage on E. to eliminate the possibility of static. get tenants to touch a clean metal part of a rad . or associated pipework just before entering bathroom.

 

[RDC1979]

Sorry should have Stated its not an electric shower it's feed from a combi boiler. Downstairs. Which is earthed as I checked.

 

[davesparks]

I'm sure it is all earthed quite nicely, you may be getting a bit too blinkered about that!

You need to identify the source of the potential difference which is causing the shock.

Did you measure the earth leakage of the installation or carry out IR testing?

I have had a similar fault where the client complained of getting shocks from the bathroom wall. There was a cable chased in the wall, a nail holding the dado rail on the other side of the wall had clipped the live. When the bathroom wall got damp with steam/condensation it would occasionally be enough to give the lady a shock when she touched the wall.

 

[marc8]

I had a fault a little while ago we had been called in had just done cross bonding & repaired the main bonding to Gas & water it was joined & broken at clamp so we through crimped & split down cable & put through clamp again all good, called back getting electric shock through sink thought hang on a minute someone is taking the ...., turned out that the pipe going from the waste was metal but looked like plastic with so much paint on it.
So they were touching taps with hand splashing in water & getting shock, it was potential difference between pipes we had cross bonded & the waste pipe, just cross bonded & hey presto all the same potential, thing is sometimes until you actually see something like this you don't think it will happen.
Also had another job similar to above lady taking a shower getting a electric shock Had BG in who disconnected circuit but could not find fault, they had a leak in flat above & was soaking the shower wall there was a light on other side of wall that was ok but above a bath class 1.
Wrong I know but it was there, anyway disconnected Earth on fitting & IR tested light ok, tested cables behind light short, separated & tested rest of cables ok to other lights but cable went down wall but not the supply cable & not cables to other lights in that room, but between light in shower & further down wall, all marble & fitted bath in the end ran in new cable disconnected old cable all ok, just shows a little damp & faulty cable in a wall can give a shock in shower.
Hope it helps

 

[Jimmyb]

I had a similar problem a few years ago, it was a wire in the wall that someone had put a screw though when fitting the cubical, it was on the boiler thermostat wire so was only live when boiler was running

 

[RDC1979]

Great advice guys thanks. I'm due back tomorrow so ill be carrying out thorough check again to find this. The landlord did have an electric shower removed and some lights taken out but loft is now boarded so looks like I may have to start there. Thanks again.

 

[davesparks]

Start with some proper testing!

 

[Charlie_]

Could be quite a few things, hope you get it sorted.
I had a similar problem a few weeks ago, turned out it was a damaged T+E running through metal stud work.

 

[telectrix]

Great advice guys thanks. I'm due back tomorrow so ill be carrying out thorough check again to find this. The landlord did have an electric shower removed and some lights taken out but loft is now boarded so looks like I may have to start there. Thanks again.

that rings alarm bells. boards = nails/screws = electrical faults.