Quick bathroom earth bonding question

[Lobster]

Amidst much gnashing of teeth I've discovered I forgot to attach bonding clamps to the shower (a) before I tiled it and then (b) before the plasterer came at the weekend to skim the rest of the bathroom. OMG. Shower valve is fed by copper pipes from above in the roof space, so I have no option but to apply earth clamps up there, and drop the cable down the cavity wall and bugger up all the new plaster to get through the noggins; thereby to connect up to the other pipework which comes up from the bathroom floor (don't ask - previous occupier had it plumbed this way!)

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.

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?

(These are all things I'd normally do, by the way; I'm just wondering if it's overkill on my part!)

Thanks David

[Lobster]

Just to clarify - I'm not talking about joining separate cables anywhere other than at pipe clamps!

David

[Andrew Gabriel]

It's probably not a good idea to end up with earth bonding clamps hidden in a wall anyway -- they would be assumed to be missing in any kind of electrical inspection.

It's good practice to avoid cutting earth bonding conductors where it can be avoided, but it's not mandatory and don't get obsessive about it. Make sure connections are good and tight.

Generally, you should bond in the room or immediately adjacent to the room. You shouldn't assume different pipes which enter the room are electrically connected outside the room -- even if they are now, they might not be in the future.

It could, and someone could fit a plastic shower in the future.

Again, don't assume continuity of pipework outside the room. Someone might do a repair with a plastic pushfit fitting or a length of plastic pipe.

[Andy Wade]

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.

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.

[Lobster]

Thanks, Andy and Andrew - that's been really helpful. (I did manage to get a single length of cable through the roofspace/cavity wall/underfloor to all necessary locations in fact, so I'm quite chuffed with that!)

Given what you say above about what does that say about where you should ideally apply the pipe clamps under the bath/sink taps: above or below the isolation valve, which we have to assume may also be a "horrible mix of boss white, hemp, PTFE and fibre washers in the way of sound electrical connection"!? Should it be above them to ensure hopefully the taps are at equal potential? (But aren't the taps' electrical continuity also still likely to be compromised by PTFE etc??) Bit confused!

David

[Andy Wade]

I'd go for below. If you bond the two pipes together (and the bath if it's metal) then there isn't going to be a voltage difference appearing between the taps, even if the electrical path through the tap connectors is somewhat resistive.

[Lobster]

Cheers, Andy: done.