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Old February 15th 20, 01:37 PM posted to uk.d-i-y
John Rumm John Rumm is offline
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First recorded activity by DIYBanter: Jul 2006
Posts: 23,516
Default Earthing through plastic pipe

On 15/02/2020 10:55, Robin wrote:
On 15/02/2020 10:45, ARW wrote:
On 15/02/2020 10:30, Robin wrote:
On 15/02/2020 09:56, ARW wrote:
On 14/02/2020 14:27, Robin wrote:
On 14/02/2020 13:53, TimW wrote:
On 14/02/2020 13:25, Robin wrote:
On 14/02/2020 11:23, TimW wrote:
On 13/02/2020 21:59, TimW wrote:
There was an ancient (1950s) steel pipe bringing mains water
into my house under the front room and then up in the cup'd
under the stairs. There there was a stop cock and it went into
copper pipe and onto the copper a large sleeved earth wire was
connected with a tag on saying "Do Not Remove".

The steel pipe was leaking so I have taken it all out and
replaced with blue plastic pipe. Was looking at the earth
arrangement and wondering if I need to earth the wiring in
another way, into the ground or something, or are we still
earthed through the water in the plastic pipe out to the
outside world?

TW

This is the supply in the porch:
https://photos.app.goo.gl/ZhguWVyk5kZkbs1X9
Two substantial earth cables from the black box, one going to
the box of trip switches, the other just dangling, redundant
from the old economy 7 circuit or something.

Can wiser eyes than mine declare the type of earthing arrangement?



That looks promising (but also a bit of a dog's breakfast).* But
I'd rather leave it to those who have seen an awful lot more of
them to advise the next step.

On a point of detail, can you see/work out where the wire
connected to the copper pipe comes from?

No, it comes from the gaps between the joists.
tw

Don't worry about that, it's trivial compared with your earthing.

The news that you have an overhead supply combined with the "dog's
breakfast" aspect makes me more inclined to suspect a "DIY PME"
installation.* That is, someone has come along and connected the
earth cable between the incomer and the consumer unit to make it
look as if you have TN-C-S/PME when in fact you have TT.

It doesn't follow that you have an exceedingly dangerous setup.
And there might be an earth rod somewhere.* But when looked at
alongside the consumer unit (with it's mix of brands and lack of
RCD protection on some circuits) I'd be bothered.* I think you
should have it looked at. But others will know more and better than
me.

In the meantime be careful.





Although it is the same service head as John Rumm's, John actually
has a Ze reading on his. However on the plus side the cut out is
sealed and that suggests that the earth is genuine. You need to cut
the seal and remove the fuse to access the earth on that service head.


My apologies to Tim for my excess of caution.

And in case Tim hasn't picked up on it, Adam does this **** for a
living - and by all accounts rather well.





It could be a false seal:-). The yellow sticker will say PME on it but
that is no guarantee. The OP's only answer is to call his supplier.




I think I was biased by the contrast with the few conversions to PME
I've seen where the earth was a short bit of cable to a MET, or to a
connector left dangling like

https://www.ukpowernetworks.co.uk/-/media/images/uk-power-networks/ge/earthing/pme-earthing-photo.ashx?h=232&w=408&la=en&hash=A5FA061E3047D5F7 76145E3CFD0CB2A81AEB15A6


I think their web site must be borked at the mo - all those links just
redirect to the home page at the moment for me...


--
Cheers,

John.

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