Yet again, I need some advice!!!!!
In my new bathroom I have plumbed-in a sink, bath and shower. Th
pipes for the bath are copper and run under the floorboards and surfac
under the bath. I have joined to these with plastic pushfit pipe an
then into 22mm flexible tap tails onto the taps. The total length o
platic pipe on this run is c. 0.3m.
For the basin, I had to run a new plastic pipe for about 1.5m whic
joins to a chromed 15mm pipe feeding the basin tap tails.
For the shower, I have run copper pipe chased into the wall and tile
over from the loft down into the power shower unit. In the loft
where they surface these pipes are connected to the HW cyliner and C
tank using plastic pipe.......
Do I need to Earth bond any/all/none of these to prevent killing me, m
wife or my children???
Oh yes..one more thing....how do I actually Earth bond them if I nee
to - on the copper pipes under the bath I carefully replaced two Eart
Clamps from the pipe, but they do not actually seem to be connected t
anything......I'm still a DIY novice (although getting more confident
are simply dont understand what those clamps ACTUALLY do!!!??
They aren't supposed to be connected to anything else necessarily, the
idea is to ensure that every exposed bit of metal is connected
together so you can't get a shock by touching two of them.
The basic requirement of the IEE regs is that all exposed conductive
'things' in the bathroom are connected together. You don't have to
include in this things like door handles and other small items unless
they have a significant chance of getting electricity connected to
them. (e.g. you do have to earth bond any bits of metal associated
with lights or other electrical fittings).
Prior to this week's bathroom refit the two sink taps were bonded
together (by the previous occupier), and so were the two bath taps,
which also were connected to the radiator - ie there were two separately
connected 'zones'. (Although there was and is continuous copper pipe
Since redoing the bonding this week, the whole lot are now connected
together (see my thread on the subject!), which I thought was necessary
according to current regs. But given that it wasn't possible to put one
hand on the bath tap and the other on the sink, was my previous setup
actually legal and safe as it was?
Start by reading and inwardly-digesting the authoritative article on the
subject, whose pictures also appear in the IEE On-Site Guide:
On this basis, you don't need to bond the basin tap tails: there's a
"long" (1.5m) length of plastic pipe between them and the incoming
metallic pipework. There's nothing else which could introduce mains
voltage (or related Harmful Potential) to those, is there. (Is there?)
The bath taps are 'almost' as isolated: though the length of plastic is
only 0.3m, it's got ordinary water, not CH-water-with-inhibitor, so the
resistance of this stretch of water is (according to the article's
figures) about 30k, two of these in parallel is still 15k. BUT you
didn't tell us whether the bath's metal or plastic, or if its waste is
metal (unlikely in anything newish). Either of those would make me
keener on bonding one of: the bath, the taps, or (if metallic) the
waste, especially if it's conceivable that the main metal pipework
feeding the bath could come into physical contact with the bath
metalwork. OTOH, if the bath's plastic, and the waste is too - leave the
The shower - now, there you have a "power shower unit", which is
electric, right (a pump rather than an instantaneous heater, yes?) So
the all-metallic pipe run from pump to shower does need to be bonded.
But, we ask, bonded to *what*? "To all the other metallic things which
are capable of introducint a potential, including a (proper,
low-resistance) earth potential."
You see, BONDING IS NOT EARTHING.
EARTHING IS NOT BONDING.
BONDING IS NOT EARTHING.
EARTHING IS NOT BONDING.
The *point* of bonding is to make EXTRA SURE that ALL of the conductive
metallic surfaces WHICH COULD BE AT DIFFERENT POTENTIALS are in fact
going to be at the SAME potential. And, therefore, no-one will get a
shock from them if they touch two or more of them at the same time, even
in the presence of a fault.
So, we don't care about a radiator fed by plastic pipework (even if it
has decorative chrome or copper pipe right by its tails), since it's not
going to be at any 'interesting' potential. In your case, that's the
argument by which we don't care about your basin taps, or your
assumed-plastic and/or far-from-metallic-pipework bath.
So, we want to bond those shower pipes to any other
potential-introducing metalwork. Well... is there any? The picture on
p.3 of the IEE article shows some common (and less common) ones - the
most obvious being yer bathroom light (or 'luminaire' as we likes to
call them in Regs-speak ;-) and a shaver socket. Other examples could
be, in a large bathroom, the washing machine and tumble-dryer you have
connected by fused-connection-units (never plugs in a bathroom!).
As a practical matter, you don't have to have a highly obtrusive and
visible green-n-yellow wire clamped to the shower pipes right next to
the controller, though. It's OK to put the clamps on the pipes in the
loft close to where they enter the bathroom, and connect the bonding
wire from there to the (say) shaver socket - either directly, or (again
more nicely) to the E terminal of the junction box which feeds the
shaver socket and the bathroom light and fan. (The Regs say it's OK to
use the 'earth wire' - the Circuit Protective Conductor - in the cables
feeding those items as the bonding conductor. But you do have to bond to
them in or close to the bathroom - no fair saying 'they're all bonded
back at the consumer unit'!)
This does raise the corner case where there's only a single
potential-introducing point in a bathroom - e.g. the all-plastic world
of pipes, non-metallic luminaire(s) with pullswitches, and just the one
(metal-faced ;-) shaver socket. In this case there's nothing to 'bond
to', since supplementary bonding means extra wiring to electically join
two or more potential-introducers. What's Good Practice in this case,
Anyway - hope that, together with the IEE article, helps. If you're left
with doubts, get a sparks in. They may well say things which disagree
with the IEE article and with what I've said, mind: the whole topic of
bonding is imperfectly understood, with some pros insisting on
festooning bathrooms (and kitchens!) with festive displays of
green-n-yellow (and in some extremes running it back to the main
earthing terminal). If you ever explore the IEE Forum where those pros
(and hangers-on) with time on their hands argue back and forth about The
Regs, you'll find supplementary bonding being one of the recurrent
topics of heated debate...
Blimey, just when I thought I'd got my head round the requirements I
read your bit above about connecting the bonding to the CPC! I'd
thought that was a complete no-no! So this is only required if you have
metal electrical fittings in the bathroom?
Right - so in my case the only exposed metal in the electrical fittings
are the screws holding on the shaver socket faceplate. Which means
there's a theoretical risk of somone being electrocuted via one finger
on a screw head and the other on the basin tap, am I right? But isn't
the risk of this so small that it would be outweighed by the 'risk (is
there one?)' of connecting the bathroom bonding to the CPC?
Nah. It's not a complete no-no: "bonding is not earthing" doesn't mean
that the bonding *mustn't* be earthed, just that its point is about
equalising *local* potentials in the bathroom, rather than providing a
low-resistance earth path. In practice your bathroom bonding is
practically always earthed, as the
metallic-things-which-might-introduce-a-potential will themselves be
The IEE guidance on CPC bonding is that it should be done even if the
equipment and wiring accessories are currently all-insulated, to allow
for later changes in what's connected.
If your basin taps are connected by metal pipework running throughout
the house - yes, they want supplementary bonding. The CPC in the shaver
socket is supposed to be supp-bonded anyway. The 'what if there's only
one thing, what does that bond to?' question I raised is a theoretical
corner-case, really - most of our bathrooms have more than one
electrical item in them anyway - although it does then get to be a bit
of an argument about whether the existing CPCs themselves provide
adequate bonding in the case where all the accessories are on the one
lighting circuit and all the cable connections are made in or close to
Stefek Zaba wrote:
Thanks for your responses to my queries in the later post in this
thread... OK, I gather I now have to extend my new bonding to include
the shaver socket then!
I already have clamps up in the loft, on the H&C pipes feeding the
shower; they are a few feet away from the jct box which provides the
feed to the shaver socket. Now - what is the correct way of wiring a
stonking great earth bonding cable into the 20A junction box!!??
Up in the loft, away from danger of mechanical damage (so clip it to the
side of joists if need be), the supplementary bonding conductor from yer
nearest pipe clamp to the shaver-socket JB (or other JB intimately
related to the things in the bathroom running off the lighting circuit)
needn't stonk ;-) It'd be acceptable, but skirting the shoals of
bodgeology, to use a length of 1mmsq/1.5mmsq lighting T&E with the L and
N conductors clearly cut short, using only the CPC. If all you have is
the 6mmsq or 10mmsq you've used for the rest of the supp bonding, you
have the choice of cutting short 4 or 5 of its strands (not such a good
plan, as it's too easy to nick the remaining strands and have your bond
fail in a few years time) or arrange a transition through one way of a
30A chockblock to a very short length of CPC-core or similar, suitably
sleeved, and clipped in place just next to the JB...
It would, wouldn't it; just that the 20A one is a 4-terminal one as it
has a switched live for the bathroom fan/light, and the outgoing circuit
cable goes to the shaver socket.
That being the case, do you subscribe to the Stefek Method, which would
be easiest!? Or should I interpose a 30A JB in the cable heading to the
shaver socket, and wire my bonding cable into that? Or summat else?
Guilty as charged - I didn't feel all that good about mentioning those
approaches in public, though I'm sure many of us have done similar, at
least in our ignorant and wayward youth ;-) The 'legit' route of going
through a 30A JB is less bodgy than the others, for sure...
If it's junction box terminal capacity that's the problem, rather than
wiring space, you could legitimately (IMO) trim two or three strands off
the end of the 4mm^2 wire. This only reduces the CSA of the supp.
bonding conductor in a space where there is mechanical protection, in
consequence of which the CSA only needs to equal that of the smaller CPC
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