Lobster wrote:

Anyway... rant over - main question: do I have to bond shower - sink -
bath - towel rail all with one continuous cable (which is what I always
do), or is that just good practice? ISTR reading somewhere that it was
mandatory but can't find anything about it now, and it will be a royal
PITA if I need to.

That's not mandatory - you just need reliable connections. The usual
rules for connections apply: screw clamps must be accessible (without
_too_ much demolition); crimps, soldered joints etc. need not be.

Secondarily - I'll bond the H&C pipes at the sink; but if I also have a
metal shower bar fed by copper pipes (no plastic anywhere in this
bathroom), do I really need to bond the H and C pipes to that as well?
Doesn't the shower valve act as conductor (or could, eg, PTFE tape in
the fittings potentially act as insulator? Indeed; do both the H&C
pipes feeding the plastic bath also really need to be bonded, given that
they will already be connected by copper pipe under the floor, by virtue
of the sink bonding?

Judgement and common sense have to be applied here. Ask yourself "could
a plumber working here easily negate the bonding?" You can rely on
short lengths of copper pipework, including soldered joints, that don't
disappear off into the distance. The bonding must be "in close
proximity to the location" as it says in the OSG. I would not rely on
continuity through compression fittings, and certainly not through tap
connectors which could interpose some horrible mix of boss white, hemp,
PTFE and fibre washers in the way of sound electrical connection.

--
Andy