Bathroom earth bonding

[Ivor Nastychestikov]

Bathroom has hot and cold water pipes, electric towel rail and an
electric shower, what bonding is required?

[Alan]

On Sat, 22 Apr 2017 10:50:44 +0100, Ivor Nastychestikov wrote:

> Bathroom has hot and cold water pipes, electric towel rail and an
> electric shower, what bonding is required?

Is everything RCD protected?
Has the incoming water pipe (and gas/oil) got bonding in place?
If so, then it is likely that there is no need for any Supplementary
Bonding.

If no RCD, or not all circuits in the bathroom are RCD protected, then
you should have Supplementary Bonding between exposed conducitve
metalwork, and the CPC of the circuit(s) in the bathroom.

[John Rumm]

On 22/04/2017 10:50, Ivor Nastychestikov wrote:

Firstly, no such thing as "earth bonding" - the phrase makes no sense.

You can have earthing, and you can have equipotential bonding. Two
different systems that work in different ways and are designed to
provide shock protection by different mechanisms. (reduced shock
duration for earthing, and reduced shock magnitude for EQ bonding).

> Bathroom has hot and cold water pipes, electric towel rail and an
> electric shower, what bonding is required?

That depends...

If the main equipotential bonding[1] is in place, and all the circuits
that feed the bathroom are RCD protected (with 30mA trip devices), then
since the 17th edition of the wiring regs, none is actually required.

If the above requirements are not met (say the lighting circuit is not
RCD protected), then you will need to equipotential bond the earth
conductors of all the circuits that feed anything in the bathroom, along
with any other metalwork that is capable of introducing a potential into
the room (and that includes an earth potential).

So typically that would include hot and cold water pipework, and
possibly central heating pipework.

You don't need to bond pipes that are plastic, or are just isolated bits
of metal "show" pipework feed from plastic pipes. Nor do you need to
bond radiators, baths or any other lump of metal that by itself is not
able to introduce a potential into the room.

You may need to bond waste pipes if they are metal and ultimately
connected to earth. (if unsure measure the resistance between them a a
known good earthing point)

For more information see:

[1] http://wiki.diyfaq.org.uk/index.php/Earthing_and_Bonding


--
Cheers,

John.

/=================================================================\
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\=================================================================/

[Ivor Nastychestikov]

On 22-Apr-17 11:34 AM, Alan wrote:
> On Sat, 22 Apr 2017 10:50:44 +0100, Ivor Nastychestikov wrote:
>
>> Bathroom has hot and cold water pipes, electric towel rail and an
>> electric shower, what bonding is required?
>
> Is everything RCD protected?

Yes.

> Has the incoming water pipe (and gas/oil) got bonding in place?
> If so, then it is likely that there is no need for any Supplementary
> Bonding.

The hot and cold water pipes are bonded to each other. The incoming
water supply enters house by a pvc pipe. There is a 4mm earth cable back
to the consumer unit, but that is not connected at the moment. There is
no oil or gas.

[F Murtz]

I have a strange situation in my bathroom, all the copper water pipes
are bonded to earth externally but I sometimes get a tingle to taps when
standing in the shower, (About 5 volts measured from metal round drain
to taps)
I can only assume that when the house was built(on concrete slab) the
reo steel in the concrete was not bonded to earth which is a requirement
today

[tabb...@gmail.com]

On Sunday, 23 April 2017 09:21:57 UTC+1, F Murtz wrote:

>
> I have a strange situation in my bathroom, all the copper water pipes
> are bonded to earth externally but I sometimes get a tingle to taps when
> standing in the shower, (About 5 volts measured from metal round drain
> to taps)
> I can only assume that when the house was built(on concrete slab) the
> reo steel in the concrete was not bonded to earth which is a requirement
> today

You need to fix that.


NT

[Scott]

Using a JCB :-)

[F Murtz]

I can not be bothered at the moment am not the slightest bit worried
that it is ever going to electrocute anyone, Some day I may jackhammer a
bit of concrete to expose some reo and bond it,

[Brian Reay]

The 5V isn't but it is a sign of something more serious- it looks like
you may have a PME earth and have 'imported' an external (real) earth.

PME earths are fine but rely on your not 'mixing' a PME earth and a real
earth in case there is a earth neutral fault- specifically a break in
the combined Neutral and Earth conductor which supplies your property.

--

Suspect someone is claiming a benefit under false pretences? Incapacity
Benefit or Personal Independence Payment when they don't need it? They
are depriving those in real need!

https://www.gov.uk/report-benefit-fraud

[tabb...@gmail.com]

On Monday, 24 April 2017 08:20:05 UTC+1, Brian Reay wrote:
> On 24/04/2017 06:53, F Murtz wrote:

> > tabbypurr wrote:
> >> On Sunday, 23 April 2017 09:21:57 UTC+1, F Murtz wrote:
> >>
> >>>
> >>> I have a strange situation in my bathroom, all the copper water pipes
> >>> are bonded to earth externally but I sometimes get a tingle to taps when
> >>> standing in the shower, (About 5 volts measured from metal round drain
> >>> to taps)
> >>> I can only assume that when the house was built(on concrete slab) the
> >>> reo steel in the concrete was not bonded to earth which is a requirement
> >>> today
> >>
> >> You need to fix that.
> >>
> >>
> >> NT
> >>
> > I can not be bothered at the moment am not the slightest bit worried
> > that it is ever going to electrocute anyone, Some day I may jackhammer a
> > bit of concrete to expose some reo and bond it,
> >
>
> The 5V isn't but it is a sign of something more serious- it looks like
> you may have a PME earth and have 'imported' an external (real) earth.
>
> PME earths are fine but rely on your not 'mixing' a PME earth and a real
> earth in case there is a earth neutral fault- specifically a break in
> the combined Neutral and Earth conductor which supplies your property.

It is indeed a hazard. A nearby strike would also put a massive voltage gradient across anyone in the shower.


NT

[Dave Plowman (News)]

In article <58fc6423$0$34633$b1db1813$15bd...@news.astraweb.com>,

F Murtz <hag...@hotmail.com> wrote:
> I have a strange situation in my bathroom, all the copper water pipes
> are bonded to earth externally but I sometimes get a tingle to taps when
> standing in the shower, (About 5 volts measured from metal round drain
> to taps)
> I can only assume that when the house was built(on concrete slab) the
> reo steel in the concrete was not bonded to earth which is a requirement
> today

Is it a wet room? I'd not expect the metal drain to be connected to
anything other than a plastic waste pipe.

I'd be inclined to check the potential between your copper pipes and true
earth. I've be surprised if you could feel 5v.

--
*Sherlock Holmes never said "Elementary, my dear Watson" *

Dave Plowman da...@davenoise.co.uk London SW
To e-mail, change noise into sound.

[Adam Funk]

On 2017-04-22, John Rumm wrote:

> On 22/04/2017 10:50, Ivor Nastychestikov wrote:
>
> Firstly, no such thing as "earth bonding" - the phrase makes no sense.
>
> You can have earthing, and you can have equipotential bonding. Two
> different systems that work in different ways and are designed to
> provide shock protection by different mechanisms. (reduced shock
> duration for earthing, and reduced shock magnitude for EQ bonding).

But they're both done with green & yellow striped cable!

[John Rumm]

Hence why they call it a Circuit Protective Conductor (CPC) and not an
"earth conductor"

You have what are classed as "fortuitous effects"; in that equipotential
bonding (by inclusion of multiple CPCs) may also lower the earth
impedance at the point of a fault and hence improve disconnection times.
Likewise earthing may add additional conductors that will also function
as eq bonding, and hence lower the touch voltages.

However these effects (while not unwelcome) may not be relied upon[1],
and each system needs to function independently.

[1] e.g. your main eq bond to the incoming water main may provide a good
additional path to earth. However it would be unwise to rely on that as
an earth since the water supplier may change it to plastic etc. So when
testing your main earthing terminal, you disconnect any bonding
connections to it for the duration of the test. Likewise eq bonding
conductors in a bathroom, don't actually need any connection back to the
main earth terminal to function correctly.

[Adam Funk]

On 2017-04-25, John Rumm wrote:

> On 25/04/2017 12:16, Adam Funk wrote:
>> On 2017-04-22, John Rumm wrote:
>>
>>> On 22/04/2017 10:50, Ivor Nastychestikov wrote:
>>>
>>> Firstly, no such thing as "earth bonding" - the phrase makes no sense.
>>>
>>> You can have earthing, and you can have equipotential bonding. Two
>>> different systems that work in different ways and are designed to
>>> provide shock protection by different mechanisms. (reduced shock
>>> duration for earthing, and reduced shock magnitude for EQ bonding).
>>
>> But they're both done with green & yellow striped cable!
>
> Hence why they call it a Circuit Protective Conductor (CPC) and not an
> "earth conductor"

I was just joking that using the same cable makes it easy for people
to confuse the two.

[ARW]

On 24/04/2017 06:53, F Murtz wrote:

I would not bother.

If anything you bond the metal waste pipe (UK regs)

--
Adam

[ARW]

I have said it before, and I'll say it again.

Bathroom electrics will one day need supplementary bonding fitting again.

RCDs are not good enough.

--
Adam

[John Rumm]

It has to be said that something that relies on a passive length of wire
and some pipe clamps is likely to be more reliable than something that
needs working electro mechanics.

[Adam Funk]

On 2017-04-26, John Rumm wrote:

> On 25/04/2017 21:45, ARW wrote:

>> I have said it before, and I'll say it again.
>>
>> Bathroom electrics will one day need supplementary bonding fitting again.
>>
>> RCDs are not good enough.
>
> It has to be said that something that relies on a passive length of wire
> and some pipe clamps is likely to be more reliable than something that
> needs working electro mechanics.

I'm struggling to imagine how it could do any harm to have more
bonding than required, as long as it's sound (i.e., not connected to
anything "bad").

[tabb...@gmail.com]

just a waste of money, some of which is used for useful purposes.


NT

[John Rumm]

Depends on your definition of more than required... if you mean
including bonding in a bathroom which meets the 17th edition exception
and hence could in theory do without, then yup no harm, and not expensive.

However some places take it to the extreme and festoon every bit of
pipework with bonding cables in places where there is not an elevated
shock injury risk. In those cases, there are probably other things you
could do with an installation to get a better return on the investment.

[ARW]

Give it 10 years before it happens:-)

Or are we looking at the thin edge of the wedge where all 17th edition
installations will have to be tested by law every ten years to check the
RCDs work correctly? Possibly after someone has died due to a failed RCD?

I do a swimming pool EICR every year and have done so for the last 5 years.

Two RCBO's have gone down in that time (they were installed 10 years ago).

--
Adam

[Roger Hayter]

John Rumm <see.my.s...@nowhere.null> wrote:

> On 26/04/2017 10:58, Adam Funk wrote:
> > On 2017-04-26, John Rumm wrote:
> >
> >> On 25/04/2017 21:45, ARW wrote:
> >
> >>> I have said it before, and I'll say it again.
> >>>
> >>> Bathroom electrics will one day need supplementary bonding fitting again.
> >>>
> >>> RCDs are not good enough.
> >>
> >> It has to be said that something that relies on a passive length of wire
> >> and some pipe clamps is likely to be more reliable than something that
> >> needs working electro mechanics.
> >
> > I'm struggling to imagine how it could do any harm to have more
> > bonding than required, as long as it's sound (i.e., not connected to
> > anything "bad").
>
> Depends on your definition of more than required... if you mean
> including bonding in a bathroom which meets the 17th edition exception
> and hence could in theory do without, then yup no harm, and not expensive.
>
> However some places take it to the extreme and festoon every bit of
> pipework with bonding cables in places where there is not an elevated
> shock injury risk. In those cases, there are probably other things you
> could do with an installation to get a better return on the investment.

My house was wired (presumably not by a professional) with 10mm^2
green/yellow wire parallelling all the T&E circuits from the CU
branching repeatedly with connection to all the pipework in every
room. Since it is all surface wiring (for structural reasons) in boxes
and trunking of various kinds I tend to strip out great reams of it
every time I redecorate or alter anything. As all circuits (except the
economy 7 one) are fast 30mA RCD protected it is hard to see what the
objective was, but it seems to imply a confusion between bonding and
circuit protection. Most of the rooms have no locally unearthed
metalwork in them apart from the central heating, which is all copper
anyway. For reasons which seem arbitrary, even earthed electrical
fittings (such as outside lights) seem often to have a parallel 10mm^2
earth connection back to the CU.


--

Roger Hayter

[Tim Watts]

I have another POV on this. I can't quote chapter and verse as I do not
have my book to hand and my memory is shite.

However, the 17th requires, IIRC, that any extraneous conductive parts
aka water pipes entering a bathroom/etc to be bonded to the main earth
as one of the conditions of not having supplementary bonding?
g
So assuming the bonding is good and equally so across all such pipes
entering the bathroom, even without an RCD, the situation is hardly
worse than if supplementary bonding were present.

As far as I can see, all supplementary bonding does is keep it all
local, reducing the chance that it gets bypassed (eg plastic pipe
sections) or a local fault exists in the CPC to say the shaver socket.


So SB makes for perhaps a more robust solution and one that *may* be
easier to verify[1] but 17th style if done correctly ought to be as
good, even if the RCD fails.


Thoughts?


[1] In reality, SB wires disappear under the floor and are often clamped
in inaccessible places like under the bath so how easy is it to verify
these, as opposed to just doing a loop test on all extraneous conductive
parts relative to the MET?

[John Rumm]

On 27/04/2017 22:19, Tim Watts wrote:
> On 26/04/17 10:58, Adam Funk wrote:
>> On 2017-04-26, John Rumm wrote:
>>
>>> On 25/04/2017 21:45, ARW wrote:
>>
>>>> I have said it before, and I'll say it again.
>>>>
>>>> Bathroom electrics will one day need supplementary bonding fitting
>>>> again.
>>>>
>>>> RCDs are not good enough.
>>>
>>> It has to be said that something that relies on a passive length of wire
>>> and some pipe clamps is likely to be more reliable than something that
>>> needs working electro mechanics.
>>
>> I'm struggling to imagine how it could do any harm to have more
>> bonding than required, as long as it's sound (i.e., not connected to
>> anything "bad").
>>
>
> I have another POV on this. I can't quote chapter and verse as I do not
> have my book to hand and my memory is shite.
>
> However, the 17th requires, IIRC, that any extraneous conductive parts
> aka water pipes entering a bathroom/etc to be bonded to the main earth
> as one of the conditions of not having supplementary bonding?

Yup the main bonding must be in place - so incoming services, and
extraneous metalwork that can distribute a potential around the building
(typically CH pipework)

> g
> So assuming the bonding is good and equally so across all such pipes
> entering the bathroom, even without an RCD, the situation is hardly
> worse than if supplementary bonding were present.
>
> As far as I can see, all supplementary bonding does is keep it all
> local, reducing the chance that it gets bypassed (eg plastic pipe
> sections) or a local fault exists in the CPC to say the shaver socket.

It keeps it local, and also electrically short - so more tightly
controlled voltage differentials.

> So SB makes for perhaps a more robust solution and one that *may* be
> easier to verify[1] but 17th style if done correctly ought to be as
> good, even if the RCD fails.
>
>
> Thoughts?
>
>
> [1] In reality, SB wires disappear under the floor and are often clamped
> in inaccessible places like under the bath so how easy is it to verify
> these, as opposed to just doing a loop test on all extraneous conductive
> parts relative to the MET?

Although the loop test does not find the metal that does enter the EQ
zone, and could be made live by a fault, but is not bonded at entry (say
a partial metal pipe install where the incoming main and initial
pipework is plastic, and hence not included in the main bonding)

[Tim Watts]

On 28/04/17 01:39, John Rumm wrote:

> Although the loop test does not find the metal that does enter the EQ
> zone, and could be made live by a fault, but is not bonded at entry (say
> a partial metal pipe install where the incoming main and initial
> pipework is plastic, and hence not included in the main bonding)

Hi John,

I need to dig out the big red book (I know..) and find the exact wording.

But from memory, doesn't the 17th say:
plumbing that is extraneous must have continuity back to the main bond,
or something along those lines.

In other words, if you have pipes entering the bathroom which do not
have continuity to the MET, then you cannot meet the conditions for not
having SB.

The one thing I am not sure of is what "continuity" means here, and I
really do need to check.

It could mean "sufficient to trip an RCD" or it could be "sufficient to
disconnect a fuse/breaker in 0.4s".


I have a 17th design, but I've got hot, cold and eventually all CH main
feeds cross bonded to each other in the hall cupboard as good measure -
mostly to ensure hot and cold pipes and radiator (when fitted) have good
continuity.

[ARW]

On 28/04/2017 08:21, Tim Watts wrote:
> On 28/04/17 01:39, John Rumm wrote:
>
>> Although the loop test does not find the metal that does enter the EQ
>> zone, and could be made live by a fault, but is not bonded at entry (say
>> a partial metal pipe install where the incoming main and initial
>> pipework is plastic, and hence not included in the main bonding)
>
> Hi John,
>
> I need to dig out the big red book (I know..) and find the exact wording.
>
> But from memory, doesn't the 17th say:
> plumbing that is extraneous must have continuity back to the main bond,
> or something along those lines.
>
> In other words, if you have pipes entering the bathroom which do not
> have continuity to the MET, then you cannot meet the conditions for not
> having SB.
>
> The one thing I am not sure of is what "continuity" means here, and I
> really do need to check.
>
> It could mean "sufficient to trip an RCD" or it could be "sufficient to
> disconnect a fuse/breaker in 0.4s".
>
>

Sufficient to trip a 30mA RCD.

Which of course may might when then the electrician did the work but may
fail when some pipework is altered (and that pipework need not be in the
bathroom).

Local supplementary bonding removes that risk.


--
Adam

[ARW]

Perhaps someone read this and got confused.

http://electrical.theiet.org/wiring-matters/26/5437-earthing.cfm?type=pdf

--
Adam

[Tim Watts]

On 28/04/17 18:22, ARW wrote:

> Sufficient to trip a 30mA RCD.

Thanks Adam.

> Which of course may might when then the electrician did the work but may
> fail when some pipework is altered (and that pipework need not be in the
> bathroom).
>
> Local supplementary bonding removes that risk.

I agree that it's more foolproof in general (with the caveats that it's
not always easy to inspect once things are panelled in).

I'm happy with my house being sans SB as it was designed with that in
mind from the get go, but I do have cross bonding straps in the cupboard
where the pipes disappear off to the bathroom - mostly to ensure
continuity remains between hot, cold and heating pipes (when they exist)
and are not reliant on the boiler manifold (when it exists) to achieve this.

I also test loop impedance is sufficient to trip the relevant MCBs in
0.4sec - I am surprised that was not written into the regs as it would
have reduced the reliance on the RCD element.

That's more identifying a likely scenario where things might get
buggered up (eg boiler removed or replaced) and dealing with that rather
than any book standard approach.

I was keen to avoid SB as I have all my pipes on show - but if that
weren't a consideration, I'd have put it in conventionally.

In fact I will possibly build SB into the shower room as the pipes are
mostly bunched in the underbasin cupboard.

[Roger Hayter]

ARW <aXXXwa...@blueyonder.co.uk> wrote:

> On 27/04/2017 20:35, Roger Hayter wrote:

snip

> >
> > My house was wired (presumably not by a professional) with 10mm^2
> > green/yellow wire parallelling all the T&E circuits from the CU
> > branching repeatedly with connection to all the pipework in every
> > room. Since it is all surface wiring (for structural reasons) in boxes
> > and trunking of various kinds I tend to strip out great reams of it
> > every time I redecorate or alter anything. As all circuits (except the
> > economy 7 one) are fast 30mA RCD protected it is hard to see what the
> > objective was, but it seems to imply a confusion between bonding and
> > circuit protection. Most of the rooms have no locally unearthed
> > metalwork in them apart from the central heating, which is all copper
> > anyway. For reasons which seem arbitrary, even earthed electrical
> > fittings (such as outside lights) seem often to have a parallel 10mm^2
> > earth connection back to the CU.
> >
> >
>
> Perhaps someone read this and got confused.
>
> http://electrical.theiet.org/wiring-matters/26/5437-earthing.cfm?type=pdf

That's a thought, but seeing it was an ordinary house and done about
thirty years ago I suspect it was just a misunderstanding of
supplementary bonding. It is a PME installation.


--

Roger Hayter

[Tim Watts]

On 25/04/17 21:45, ARW wrote:

> I have said it before, and I'll say it again.
>
> Bathroom electrics will one day need supplementary bonding fitting again.
>
> RCDs are not good enough.

It's worth noting (from the Red Book, I've mislaid my green):

701.415.2

"
...
Supplementary equipotential bonding may be installed outside or inside a
room containing a bath or a shower, preferably close to the point of
entry of extraneous conductive parts into such rooms."

(I'd be grateful to know if that wording remains in the latest 17th?)


...So you don't have to make a mess of a tiled room and have clamps on
show everywhere to meet SB.



I've been thinking about your argument Adam, and it is persuasive. And I
would not be surprised either if they revise it - maybe in 10 years when
a couple of people who never test their RCDs have got a belt.


I am going to build SB into my shower room (we're laying the floor
screed for that in 2 weeks) - that's really trivial as the shaver socket
and pipes all pass through to or back onto the lobby cupboard so the
clamps can go there.


I am tempted, at some point to add SB back to the main bathroom at some
point. The 17th exemption seemed like a good idea at the time, but...

Only problem there is the SB runs are tortuous. Pipes exit under the
stairs 1m from bathroom - that's OK, convenient and fairly obvious
clamping point. But to get to shaver socket and bit of pipe to high
level loo cistern (if that's in the zones, have to check) require going
up through the ceiling and some 5-7 metres around. It would work and I
can see nothing in the regs that precludes this - it just won't be
terribly obvious what's going on to anyone else.


What's your opinion on that (long SB wire routing)?

Cheers,

Tim

[ARW]

It's possible to work out a maximum touch voltage between two metallic
objects (one at 230V and one at 0V) bonded by a 4 mm earth cable.

However I have been in the pub for 6 hours (mt apologies to Wakefield)
and I'll pass on trying that calculation today.





--
Adam

[Tim Watts]

Thanks Adam.

If that's all it comes down to, fair enough.

However, the potential difference would also depend on what's connecting
the Ov and 230V sides. 4mm2 is not much compared to the area of copper
in a 15mm water pipe which is about 32mm2 for 0.7mm walled pipe.

OTOH 4mm2 is vastly larger than the 1 - 1.5mm2 CPC in the lighting
circuit which also has a long run to origin.


Less true with a shower though that might have a 4mm2 CPC and larger
live conductors.


So how is the theory of supplementary bonding handled? Presumably some
allowance must be made for ADS being operational?

[ARW]

You keep the touch voltages between two objects to less than 50V.

If the ADS is still working in 10 years time (ie the RCDs) then fine.


The maximum potential difference with EEBADs is down to the resistance
of the 4mm cable between the two points connected by that cable.

And yes I would expect an MCB or fuse to trip before this sort of thing
happened.

No matter what you design for some pillock will still manage to mess it up.


--
Adam

[tabb...@gmail.com]

PSCC of domstic wiring is anything upto 6kA.
4mm2 voltage drop is 5.5mV/A/m or 5.5v/kA/m
You can calculate from that, adding in the R of the supplying lighting circuit.


NT

[ARW]

Mine is >12kA.


--
Adam