Andy Wade wrote:
Chris J Dixon wrote:

Do pipework bonds have to be both visible

No.

and accessible?

Yes, unless soldered, welded or crimped, etc. Joints relying on
screw
terminals should be accessible.

If simply accessible, do the same sort of conditions governing the
use of junction boxes apply (e.g. removable floorboards)? What
about
under the bath?

The same rules apply as for live conductors, yes. "Accessible" isn't

defined in BS 7671 and is open to interpretation - anything is
accessible if you demolish enough of the building! Use common sense
-
anything requiring destruction or inconvenience out of proportion to
the
task of accessing the connection isn't compliant, IMO.

Is this influenced by whether or not tools are needed for access,
or
does that only affect the need for bonding?

That surely affects neither.

When connecting to the various CPCs, presumably at existing
fittings, or junction boxes (can't quite see 4mm cable being
accommodated in a light fitting) is there a requirement for
identification somehow?

Identification of the bonding conductor as a protective colour is by
means of the green/yellow colour. The "safety electrical connection
-
do not remove" label is only required, in this context, at
connections
to extraneous-conductive-parts (i.e. non-electrical stuff like
pipework); it's not required on bonding connections to
exposed-conductive-parts or CPCs.

The 4mm^2 size is only needed if there's no mechanical protection.
An
enclosed bonding conductor on to the CPC of a normal lighting or
shaver
point circuit can be 1mm^2 (for circuit cables up to 1.5mm^2) - and
of
course you are allowed to use the CPCs as the bonding, provided that
they remain "in close proximity to the [bathroom] location". So on
the
lighting circuit it's often more practical to bond to the earth
terminal in the switch enclosure than in a luminaire.

So far as I can see, it is quite OK for the underfloor bonding
and the ceiling bonding to be joined only by a common length of
pipe. Is this right?

Debatable. Reg 547-03-04 allows conductive parts "of a permanent and

reliable nature" to be used as part of the bonding. If you think a
plumber could come along and replace the pipework in question with
plastic and not realise that any bonding would need to be patched
then,
IMO, that regulation couldn't be applied. (IOW, if in doubt, bond
separately.)

HTH
--
Andy

I am a bit sceptical about this accessibility issue. How many people
have mains and lighting connectors under their floorboards, I suspect
many of us, and how many have carpets, flooring etc. on top.
, so not really accessible. I have heard the arguments about copper
creep etc. but over the last 15 years of owning a house I havce never
had to rip anything up to find a fault with ring main/lighting circuit.
Am I just lucky?