On Sat, 22 Apr 2017 10:50:44 +0100, Ivor Nastychestikov wrote:
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
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.
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.
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).
If the main equipotential bonding 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:
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
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
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
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 firstname.lastname@example.org London SW
Hence why they call it a Circuit Protective Conductor (CPC) and not an
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,
and each system needs to function independently.
 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.
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.
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