damp wall shocks

[henry hill]

recently moved into a new house that has recently been refurbished.
everything ok for a couple of of weeks but recently have been getting shocks off kitchen sink and bath taps. Outside there are security grilles over the windows and these too have been giving shocks. All of the problems are isolated and only occur on 1 wall, both inside the house and outside.

noticed that there was a damp patch on the kitchen ceiling underneath the bathroom. upon investigation (removing bath panel) found that bath perimeter seal was inadequate and that water was leaking down the tiled/plastered wall behind the bath. have sealed the bath/tiles with silicone and cured the leak problem. However, the wall is still damp and whenever I touch the bath taps and tiles simultaneously I get a shock. Similarly whenever I touch either the kitchen sink taps/stainless steel sink and plaster wall in the kitchen I get a shock.

I have borrowed a multi meter from my Dad. there is no problem with the pipework serving the boiler or the basin in the bathroom and all of the pipes on the hot and cold water pipes serving the kitchen sink and washing machine, the basin and the boiler in the bathroom are ok. Its just the one wall where the water has been leaking. all of the pipes have metal clamps n with green/yellow sheathed cable (including all of the pipes on the boiler)

I turned off the electric at the fuse box.. no problem.
I turned on the downstairs sockets fuse only... problem.
I did the same individually with the lighting circuit and 1 labelled "immersion" (this operates the combi boiler only which I have been told is less than a year old) and there is a problem with both.
only the upstairs sockets when on all other circ uits off do not give a shock.

??? why is this happening???
???is it just because the wall is damp??
??or is it indicative of a more serious problem???

there wasnt a problem at all for 2 1/2 weeks untill last sunday.

??? is it likely to stop as the wall dries out??

Have had the dehumidifier on all week.

Please advise!!

 

[luminaire]

What type of supply do you have, is it one of these ?

Do you have main equipotential bonding - i.e. your at your gas meter and at your stop cock?

 

[henry hill]

the electric and gas meters are both in outside boxes and both have green and yellow sheathed cable disappearing inside the house. The stop cock is hidden begind a plastic louvred vent in the basement (it has had wooden studded walls and plasterboarded out. I have had a feel for an earth clamp but cant feel one. I do not know where the sheathed cable goes to. presumably to the fuse unit. All have switched fuses (rcd's??? mcb's??? all of the bathroom copper piping have got sheathed green/yellow cable near the taps and all of the boiler pipes have it too sort of daisy chained together and the sheathed cable goes underneath the tiled bathroom floor.

 

[henry hill]

from the diagram (link that you posted) i presume there should be 3 earth cable going to the consumer unit??? 1 each from electric meter, gas meter and water??? is this correct? I am unsure about taking the front off the consumer unit!!!

 

[luminaire]

The one from the electricity meter should be 16mm² and the two from gas/water 10mm².

You may have to call in an electrician to make sure there is a positive connection here on your earthing.
Does it say somewhere close to your meter PME?
(Protective Multiple Earthing)

 

[JohnD]

can you post a pic showing the Meter, the Consumer Unit, the supplier's incoming cable and service head which contains a fuse, and the various cable around and between them all.

Look around your meter for a label saying "Protective Multiple Earth"

Do you have an underground electrical supply, or overhead?

Look for any signs of a screw or nail into wall, floor or ceiling that might have penetrated a cable. Especially near the damp wall.

You say you have a multimeter. Check for AC voltage, and for continuity, between all the metal pipes you can find, taps, radiators, and the earthing of each electrical circuit (you can do this without unfastening anything, just touch the probe tip to the metal screw which holds the switchplate or socket into its metal box) and to the metal earth clamps you mention on the main services. You will need an extension cable to the meter, but you can use a piece of flex (unless you have some other insulated wire handy). Take care not to touch any exposed metal while you are doing this as you may get a shock. There should be continuity between all of them, and no voltage

In case it is not an easy DIY fix, start asking round friends and neighbours for a recommended local electrician.

 

[henry hill]

ok thanks a lot ppl. I'll try it out and get a sparks in to have a look. thanks again will keep you posted.

 

[JohnD]

I am coming to the view that there is a damaged cable in that wall, probably with a nail through it, which is making the damp wall live.

 

[bernardgreen]

This copuld be one of two things,

[1] pipe work is true earth and the damp wall has a bare live wire or terminal buried in the plaster or similar ( I once found a backing box live due to a trapped wire making a damp wall live )

[2] the damp wall is true earth and the pipe work has lost its connection to true earth and is floating.


Using a metal stake in damp ground as a true earth measure the voltage between that and water pipes in the house. It should be less than 25 volts and prefereable less than 5 volts. If it is more then the earthing to the house has failed somewhere.

 

[Coniferman]

Have had the dehumidifier on all week.

Do you know what the humidity is? Does it have a humidity control? If the house is too dry you might just be getting static shocks????

 

[oharaf]

I would agree that somewhere there is a spiked cable with a screw/ nail.

This would make the wet wall live, even if it is dry it can still be live!!!

Our decorator placed some plastering angle near the kitchen switch feed, he accidently pushed it through the PVC without noticing.

Johnnny plasterer came that weekend let him self in to do the plastering happily plastered away until he reached the edge. Took the lot straight through his all metal trowel.

Then went back to smooth off the rest of the wall hay presto, one smooth sweep with the supply alll the way through him.

Bought him a pint next day had terrible shakes mind!!!

Switch power off, sweep the wall with cable/ stud locator pay special attention to the verticals and horizontals near your switches and sockets!!!

bol