Earthing a bath

[ban-all-sheds]

Not earthed, but a bath turned from something not part of the electrical installation to something that is.

Why would you want to electrify the bath if you didn't need to?

 

[Paul_C]

When doing so is better than the alternative of a fault condition resulting in a dangerously high voltage existing between it and other bonded pipework which is within reach.

 

[ban-all-sheds]

How are you going to get a potential difference between the bath and something else?

 

[bernardgreen]

How are you going to get a potential difference between the bath and something else?

Suppose

[1] the bath has a conductive path to true earth ( the ground ) and the pipe work is connected to the CPC which is derived from the incoming neutral. Then there is network problem and the neutral bounces up to a potential above true earth.

[2] the floor that the bath is on becomes damp and a conductive path to the live conductors in the ceiling rose of the room below is created.

[3] accidental connection of live electricity to the bath due to foolish use of electrical appliances in the bath room.

I agree the chances of these happening are small and with a poor conductive path the risk of death by electrocution is small ( but not insignifcant )but the risk of consequential injury due to a non fatal shock is significant.

For the time and effort needed to bond the bath I consider it is worthwhile benefit to bond the bath to the pipe work.

 

[ban-all-sheds]

[1] the bath has a conductive path to true earth ( the ground )

If it did then there would be no argument about it being an extraneous-conductive-part and therefore requiring bonding.

The OP says that he has looked into all of this, and all he can come up with is "I definitely need to earth the bath as it could potentially become live under a fault condition", so in other words it is not an extraneous-conductive-part, the bath does not have a conductive path to true earth ( the ground ).

[2] the floor that the bath is on becomes damp and a conductive path to the live conductors in the ceiling rose of the room below is created.

Try to stay within the bounds of the sensible. How is a damp floor going to create a conductive path to the ceiling rose of the room below?

[3] accidental connection of live electricity to the bath due to foolish use of electrical appliances in the bath room.

Go away.

For the time and effort needed to bond the bath I consider it is worthwhile benefit to bond the bath to the pipe work.

I consider connecting an isolated item to the electrical installation crazy.

 

[bernardgreen]

You may have your opinion and you are welcome to have it.

Others may dis-agree, please accept that.

I do recall that the waste pipe of the bath in my mother in law's house was metal and connected to a metal soil stack pipe that entered the ground. So that bath was connected to ground and as you say

extraneous-conductive-part and therefore requiring bonding

So there we agree,

I consider connecting an isolated item to the electrical installation crazy.

So the water stop cock under the kitchen sink with plastic pipe work on both inlet and outlet. Is it crazy to bond that as per the regulations.

And people do do foolish thing with appliances in bathrooms.

And wet floors can make conductive paths to live conductors. One extreme example was a floor board nail touchling the live of a badly installed cable. Went unnoticed until water was spilt on the carpet from a radiator and a person bending down to mop it up and holding the radiator got a shock. Not fatal but extremely frightening.

Perhaps earthing the radiator was the wrong thing to do as that contributed to the circuit for the shock.

 

[JohnW2]

[2] the floor that the bath is on becomes damp and a conductive path to the live conductors in the ceiling rose of the room below is created.

Try to stay within the bounds of the sensible. How is a damp floor going to create a conductive path to the ceiling rose of the room below?

[3] accidental connection of live electricity to the bath due to foolish use of electrical appliances in the bath room.

Go away.

I have some sympathy with your viewpoint, but one has to remember that the regulations contain many requirements which are seemingly based on some incredibly improbable eventualities.

For the time and effort needed to bond the bath I consider it is worthwhile benefit to bond the bath to the pipe work.

I consider connecting an isolated item to the electrical installation crazy.

As far as I'm aware, no-one is suggesting any direct connection to the electrical installation (e.g. a connection to a CPC), merely a bonding connecting between metalwork and pipes (which may, or may not, be in electrical continuity with the MET) - in order to ensure that potential differences (however improbable) do not exist.

Since, (in the absence of plastic pipes/fittings) metal pipework generally will be connected to the electrical system (via main bonding) are you suggesting that it would be crazy not to take steps to isolate that pipework from the electrical system - e.g. by the use of plastic inserts?

Kind Regards, John.

 

[bernardgreen]

but one has to remember that the regulations contain many requirements which are seemingly based on some incredibly improbable eventualities

And at the same time ignore some of the more probable scenarios. Such as a double insulated hand held food mixer being dropped into a stainless steel sink full of water while still plugged in.

And the outside water tap bonded to the MET and thus at a different potential to the wet ground underneath it.

 

[JohnW2]

but one has to remember that the regulations contain many requirements which are seemingly based on some incredibly improbable eventualities

And at the same time ignore some of the more probable scenarios. Such as a double insulated hand held food mixer being dropped into a stainless steel sink full of water while still plugged in.

Indeed.

And the outside water tap bonded to the MET and thus at a different potential to the wet ground underneath it.

That pd should obviously be minimised by the bonding of the MET to the incoming water supply pipe, which ought to also be in contact with that wet ground. However, I agree that the DNOs 'earth' will probably have a much lower impedance than the connection through earth between supply pipes and the wet ground beneath the tap - and therefore would normally 'win' and result in a potentially hazardous pd such as you describe. It would obvioulsy be preferable (safer) if outside taps had to be electrically insulated from the house's internal (bonded) pipework.

Kind Regards, John.

 

[ban-all-sheds]

You may have your opinion and you are welcome to have it.

Others may dis-agree, please accept that.

There's disagreement with an opinion.

And then there's having funny ideas about what makes things safer. Or not.

I do recall that the waste pipe of the bath in my mother in law's house was metal and connected to a metal soil stack pipe that entered the ground. So that bath was connected to ground and as you say

extraneous-conductive-part and therefore requiring bonding

But the OP's bath is not and does not.

So there we agree,

Do we agree that the OP's bath is isolated?

So the water stop cock under the kitchen sink with plastic pipe work on both inlet and outlet. Is it crazy to bond that as per the regulations.

If you bond as per the regulations you would not bond it.

And people do do foolish thing with appliances in bathrooms.

People do all sorts of foolish things with all sorts of foolish things in all sorts of places.

Some people, for example, do foolish things in bathrooms with cable and clamps to connect isolated items to their electrical installation.

And wet floors can make conductive paths to live conductors. One extreme example was a floor board nail touchling the live of a badly installed cable. Went unnoticed until water was spilt on the carpet from a radiator and a person bending down to mop it up and holding the radiator got a shock. Not fatal but extremely frightening.

Perhaps earthing the radiator was the wrong thing to do as that contributed to the circuit for the shock.

So in that example, what would have been safer - a completely isolated bath or one that was connected to extraneous-conductive parts and installation cpcs?

 

[ban-all-sheds]

As far as I'm aware, no-one is suggesting any direct connection to the electrical installation (e.g. a connection to a CPC),

As far as I'm aware supplementary equipotential bonding does involve connecting extraneous-conductive-parts to the cpcs of the circuits supplying equipment in the room...

Since, (in the absence of plastic pipes/fittings) metal pipework generally will be connected to the electrical system (via main bonding) are you suggesting that it would be crazy not to take steps to isolate that pipework from the electrical system - e.g. by the use of plastic inserts?

It would be better to not have e-c-ps.

Whether it is as crazy to not remove any that you have as it is to pretend you have ones that you don't.....

 

[JohnW2]

As far as I'm aware, no-one is suggesting any direct connection to the electrical installation (e.g. a connection to a CPC),

As far as I'm aware supplementary equipotential bonding does involve connecting extraneous-conductive-parts to the cpcs of the circuits supplying equipment in the room...

It does indeed, and maybe I'm not right in saying that no-one is suggesting it - but I think we are all agreed that 'supplementary equipotential bonding' (per BS7671) is not required in the op's situation. If you look at my posts, you'll see that I, for one, have not been talking about 'supplementary equipotential bonding' (which is a concept of BS7671, and not required in the op's situation) - but, rather, about common-sense bonding together (but not to cpc) of pipework and metalwork that can be simultaneously touched.

Kind Regards, John.

 

[ban-all-sheds]

If the pipes and taps are e-c-ps, then they will be connected to the cpcs.

If you connect the bath to the pipes and taps then you will be connecting it to the cpc's as well.

 

[JohnW2]

If the pipes and taps are e-c-ps, then they will be connected to the cpcs.

Internal pipes and taps obviously cannot actually be extraneous conductive parts, as defined in BS7671, since they cannot in themselves be "liable to introduce a potential into the building" (since they are entirely contained within the building). The incoming water supply pipe will usually be an e-c-p and therefore will require main bonding to the MET - but in the presence of plastic pipes/fittings (and the absence of any other explicit bonding) the pipes and taps within the house will not necessarily be connected to that e-c-p or the MET/CPCs.

If you connect the bath to the pipes and taps then you will be connecting it to the cpc's as well.

Indeed. If there are no 'plastic interruption issues', then that will usually be the case....

...so, as I asked before, do you therefore think we should be obliged to insulate pipes and taps within the house from the incoming e-c-p? If not, why do you regard it as 'crazy' to have the bath so connected, whilst accepting that the regs usually result in that being the case with the taps, pipes and radiators? ... or what?

Kind Regards, John.

 

[ban-all-sheds]

Internal pipes and taps obviously cannot actually be extraneous conductive parts, as defined in BS7671, since they cannot in themselves be "liable to introduce a potential into the building" (since they are entirely contained within the building).

If that is the case then they do not require bonding.

The OP's pipes are bonded, so we have to assume that they are e-c-ps.

If they are not, and yet someone has still bonded them, I put it to you that the concerns expressed here about a potential difference arising between them and the bath shows just why it does not increase safety to take parts which are not e-c-ps and connect them to the electrical installation.

The incoming water supply pipe will usually be an e-c-p and therefore will require main bonding to the MET - but in the presence of plastic pipes/fittings (and the absence of any other explicit bonding) the pipes and taps within the house will not necessarily be connected to that e-c-p or the MET/CPCs.

Then if there is no other way for the pipes and taps to introduce a potential they are not e-c-ps and BS 7671 does not require them to be bonded.

so, as I asked before, do you therefore think we should be obliged to insulate pipes and taps within the house from the incoming e-c-p?

Obliged?

Probably unjustifiable.

If not, why do you regard it as 'crazy' to have the bath so connected, whilst accepting that the regs usually result in that being the case with the taps, pipes and radiators?

The regulations only result in pipes being connected to the cpcs if the pipes are e-c-ps.

If they are not e-c-ps then they do not require bonding, and therefore do not end up connected to the cpcs.

Is the OP's bath an e-c-p?