dave wrote:

Hang on. You say I am "mighty confused" based on the assumtion that *you think*
I *may* be confusing the means of earthing with an equipotential bond!

No, I only said you _seemed_ (to me, at that point) confused about many
aspects of the subject. The other source of possible confusion, between
earthing conductors and bonding conductors, has been common in threads
like this, so it helps if it's resolved early in the discussion, that's
all.

[...]

Well of course it would be to install NOW. That's why I clearly stated the age
of the property. Do you think I ripped out the PME and installed a equipotential
bond to the water supply in place of it? My actual question was, is it illegal
NOW. It may well be unsafe - that's clearly a separate point. (remember the RCD
though).

I know of no reason which makes it illegal now. The building
regulations, Part P of which which now cover the electrical
installations of dwellings, are not retrospective.

Right now it requires urgent investigation and
possibly remedial work.

That's right. The past 30 years it's been teetering on the edge of black-hole
collapse. Yes I know that just because it's been a long time doesn't mean it
safe etc etc. Anyway, that's what I'm "looking at" now.

So long as the water service pipe remains metal and provided that the
RCD is regularly tested to ensure it works, then it's probably not
electrically unsafe (although any competent electrician doing a PIR
would flag it as 'code 1' - "requires urgent attention" - if only to
cover their own arse).

It also sounds as if you have a single whole-house RCD (30 mA?) and
that, nowadays, is not regarded as a safe arrangement since a single
earth fault will result in loss of supply to all circuits, including
lighting, which may be dangerous (trip/fall hazards) and will almost
certainly be inconvenient.

[See reg. 314-01-01 of BS 7671 which says:
"Every installation shall be divided into circuits as necessary to:
(i) avoid danger and minimise inconvenience in the event of a fault,
and
(ii) facilitate safe operation, inspection, testing and maintenance."]

For upgrading you have two earthing options, either install a proper
earth electrode (usually one or more rods), keeping it as a TT system,
or get the supply and installation upgraded for PME. At the same time
you could consider replacing or upgrading the consumer unit to provide a
split-load arrangement complying with 314-01-01. For TT this should
usually have a 100 mA RCD for all circuits except those socket circuits
"reasonably expected to supply portable equipment for use outdoors,"
which must go via a 30 mA RCD [reg. 471-16-01]. For a TN system only
the latter, 30 mA, RCD is required.

A closing thought is that I may not be allowed to do it anyway - given the
latest legislation.

Part P doesn't forbid DIY wiring work of any kind. If the work
concerned is notifiable then a building notice should be submitted to
the local authority, who are supposed to arrange for inspection, testing
and certification of the completed work. For non-notifiable work you
are responsible for doing (or arranging) your own inspection, testing
and certification. Installing or upgrading equipotential bonding is not
notifiable work, but altering the earthing arrangements and consumer
unit replacement are notifiable.

--
Andy