That's the problem with specialists of course: a humble DIYer like myself has to take most of what they say on trust, at least until it can be checked by posting on here and getting a discussion like this one going.
It has underfloor heating throughout, with copper pipework above ground and flexible plastic leading off from the manifolds.
Many thanks for such a detailed reply, John.
Bert
Only the oldest of properties are served by metallic pipe. It used to be iron/lead. Never copper outside the property.
Iron rusts and lead is valuable and alkathene has been around long enough to have replaced most of them.
it is inert, its cheap, its flexible, and it is stable. What's not to like?
The incoming supply cable does appear to have had its outer protective metal sheathing cut right back though, with only the inner part entering the suppliers cutout.
And if Bert says all the original wiring has been replaced, why is there a warning notice about mixed colours ?.
Phone and aerial typically don't count. The rule of thumb is to assess if the service is capable of introducing a potential into the property - typically where that potential is that of the (local) earth.
If it is, then it should be bonded to the electrical earth so that there is no (or limited) potential difference between them. That way there is no possibility of say touching the metalwork of an earthed electrical appliance at the same time of say an earthed water pipe, and getting a shock because they are not at the same earth potential (possibly due to electrical fault elsewhere).
Which suggests the water pipe would not need bonding - although it is common to see a bond to just before the main internal stopcock if it is copper at that point.
(your report suggested that there was a bond to the cold water main)
I should have been clearer: the new wiring was all beyond this point.
Bert
I thought it was *always* (i.e. since time immemorial) to connect earth to a gas main pipe. I almost commented when I saw the original posting.
Equipotential bonding doesn't necessarily go to 'system' earth does it? The whole (sole) point of equipotential bonding is to ensure that all lumps of metal (i.e. conductors) that you can touch have no voltage between them.
That lost a 'not allowed' or 'a no no' after the *always*. :-)
When my new electric and gas meters were installed, they noted a lack of equipotential bonding on the gas pipes, however, it is there, but for neatness, is connected under the floor ... as are the water pipes.
It is still (and always has been) allowed to connect to a gas pipe to form a main equipotential bond. However you are no longer allowed to rely on the gas pipe connection alone as a main earth connection in a TT install. So you would need a dedicated earth spike (or grid or whatever), plus equipotential bonds to gas, water etc. The eq bonds may give some fortuitous earthing, but that is a bonus, not a replacement for a proper earth.
Main equipotential bonding *does* connect incoming services and the main earth. Supplementary equipotential bonding does not need (directly) connecting to the earthing system - it will function in isolation.
(although it may well en up with a de-facto connection to the earthing system via the CPC of any circuits present in the room with bonding since they need to be included in it)
... and now the tables are turned because the gas pipe has to be bonded where it enters the premises.
I'm happy to report that this is now - I think - resolved. In the main it seems to have been a saga of misunderstandings, misinterpretations, and basic ignorance (some of it on my part). Many thanks to everyone who chipped in.
Bert
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