Earthing Steel Bath

[A1Dan]

Apologies if this is similar to other threads, but I couldn't see anything explicitly for this situation...

I'm installing a steel bath, with polypipe plumbing / plastic waste - ie no metal joining to it. It is replacing an acrylic bath, and there is no earthing in place. It's also quite a long way to anything earth points - shaver socket a couple of metres away is the nearest thing.

Do I need to earth the bath, and if so, are there any specific details?

 

[dann09]

Transfer your post to the Electricians forum.

There are a number of Q's ref your particular situation, but briefly, we now have the 17th Ed. of Elec regs and all elec work, devices, etc in a bathroom require an RCD to be in place, or to be fitted.

Ask the mods to transfer you, and the sparkies will take you thro it.

 

[matt1e]

In short No it would make for a potentially unsafe situation

Matt

 

[A1Dan]

Transfer your post to the Electricians forum.

There are a number of Q's ref your particular situation, but briefly, we now have the 17th Ed. of Elec regs and all elec work, devices, etc in a bathroom require an RCD to be in place, or to be fitted.

Ask the mods to transfer you, and the sparkies will take you thro it.

I thought that might be the answer, but the (annoying) thing is that I'm not doing any electrical work, just putting a new bath in!

We don't have an RCD in place, but it seems excessive to have get a sparky in just because I'm replacing my bath?!

 

[matt1e]

We don't have an RCD in place, but it seems excessive to have get a sparky in just because I'm replacing my bath?!

Having an RCD in place or not doesn't come in to it
as already said, DO NOT bond the bath, there is no requirement to in your situation and to do so would make you more likely to receive an electric shock should a fault occur.
also as said, post this in, or get a mod to move it to the electric section for peace of mind

Matt

 

[sooey]

I agree with matt, if it's supplied by plastic pipes you shouldn't earth it.

 

[OwainDIYer]

Baths are NOT earthed.

What needs to be provided, in electrical installations to 16th Edition, or in electrical installations to 17th Edition lacking RCD protection on all circuits in the bathroom, is equipotential bonding of all metallic services entering the bathroom.

Unless your metal bath is protruding through a hole in the bathroom wall it does not need bonding, as there is no possibility of it introducing a voltage from outside the bathroom.

 

[dann09]

We dont yet know what kind of bath is being proposed.

What if it's a Whirlpool or Jacuzzi type tub? The pump motor will require earthing.

What if there are other "what if's" that the OP's not mentioned (very common IME) that might come out if a sparky took the OP thro a few relevant questions?

 

[dann09]

I've just noticed that we are now in the electrical forum.

 

[EFLImpudence]

Strictly speaking the only way to tell definitively is to do an insulation resistance test between the bath and the MET after installation of all equipment.
A reading in excess of 23kΩ will mean the bath does not need bonding.
It should never be earthed.

However, if it is supplied by plastic pipes and has a plastic waste with no electrical items connected to it (and is not stood on a wet muddy floor) then it will not require bonding as there will be nothing to bond to it.

'Bond' does not just mean 'connecting'.
It means equalising potential between extraneous-conductive parts.
If the bath has no potential then it must not be equalised with parts that do.

 

[RF Lighting]

Hooray. Someone who actually understands earthing and bonding!

 

[JohnW2]

Strictly speaking the only way to tell definitively is to do an insulation resistance test between the bath and the MET after installation of all equipment. A reading in excess of 23kΩ will mean the bath does not need bonding.

As previously discussed, I don't disagree with that conceptually, although I'm personally not all that happy with essentially arbitrary criteria (i.e."10mA", at the time of measurement). If it were my house, if the measured resistance (to MET) were 'as low as', say, 25kΩ,or even 50kΩ, I think I would probably want to investigate the reason, since it might be due to something which, under certain environmental/weather conditions could fall to much less than 23kΩ.

However, and more to the point, I think that some may read your statement as implying that a measured resistance <23k&#937; means that bonding is required - e.g. (per your measurement to MET) that bonding of the bath would be required if, for example, it were plumbed in copper (almost inevitably with a low resistance to MET).

Kind Regards, John

 

[EFLImpudence]

As previously discussed, I don't disagree with that conceptually, although I'm personally not all that happy with essentially arbitrary criteria (i.e."10mA", at the time of measurement). If it were my house, if the measured resistance (to MET) were 'as low as', say, 25k&#937;,or even 50k&#937;, I think I would probably want to investigate the reason, since it might be due to something which, under certain environmental/weather conditions could fall to much less than 23k&#937;.

Yes, but it is merely an arbitrary figure derived from 10mA which is deemed 'safe'.
Should you disagree you may use 5mA and 46k&#937;.

However, as I have said before, the actual reading is not likely to be a choice between 22,999 and 23,001 it will either be relatively low because of other connections or relatively high - maybe infinity.
It would be extremely unlikely to be exactly 23,000&#937; leaving you in a quandary.

However, and more to the point, I think that some may read your statement as implying that a measured resistance <23k&#937; means that bonding is required - e.g. (per your measurement to MET) that bonding of the bath would be required if, for example, it were plumbed in copper (almost inevitably with a low resistance to MET).

I'm not sure of your exact point.
Do you mean because the pipes are already bonded?

 

[JohnW2]

As previously discussed, I don't disagree with that conceptually, although I'm personally not all that happy with essentially arbitrary criteria (i.e."10mA", at the time of measurement).

Yes, but it is merely an arbitrary figure derived from 10mA which is deemed 'safe'. Should you disagree you may use 5mA and 46k&#937;.

I'm happy enough with 10mA - which will be 'safe' for the vast majority of people (give or take consequential injuries due to 'jumps'/falls etc.). My concern relates to the fact that this resistance (hence the 10mA) is a measurement made at one point in time, under the pertaining environental conditions. If one ever did measure a resistance anything like as low as, say, 24k&#937; (which I agree is very unlikley), it could, as I said, be due to something (e.g. a metal waste pipe which penetrated soil) which could fall to a much lower resistance at other points in time.

However, as I have said before, the actual reading is not likely to be a choice between 22,999 and 23,001 it will either be relatively low because of other connections or relatively high - maybe infinity. It would be extremely unlikely to be exactly 23,000&#937; leaving you in a quandary.

Indeed - which is why I wonder whether it may not make more sense for the 'rule' ('of thumb') to talk in terms of a figure very much higher than 23k&#937; - maybe 0.25M&#937;, 0.5 M&#937; or even 1M&#937;.

However, and more to the point, I think that some may read your statement as implying that a measured resistance <23k&#937; means that bonding is required - e.g. (per your measurement to MET) that bonding of the bath would be required if, for example, it were plumbed in copper (almost inevitably with a low resistance to MET).

I'm not sure of your exact point. Do you mean because the pipes are already bonded?

I'm saying that copper pipework is almost inevitably going to have a low resistance to the MET - due to CPCs ,quite apart from bonding. Connect such pipework to a metal bath and the metal bath will have a resistance <<23k to the MET - and your statement could be taken to mean that it therefore needs to be bonded.

Kind Regards, John

 

[EFLImpudence]

I'm happy enough with 10mA - which will be 'safe' for the vast majority of people (give or take consequential injuries due to 'jumps'/falls etc.).

23k&#937; is the cut-off point, then.

My concern relates to the fact that this resistance (hence the 10mA) is a measurement made at one point in time, under the pertaining environental conditions. If one ever did measure a resistance anything like as low as, say, 24k&#937; (which I agree is very unlikley), it could, as I said, be due to something (e.g. a metal waste pipe which penetrated soil) which could fall to a much lower resistance at other points in time.

But a metal waste will be bonded so the value will be very low.
You don't need to measure a metal waste in the ground - it should be main bonded.

An isolated bath isn't going to change unless someone does something to change it.

Indeed - which is why I wonder whether it may not make more sense for the 'rule' ('of thumb') to talk in terms of a figure very much higher than 23k&#937; - maybe 0.25M&#937;, 0.5 M&#937; or even 1M&#937;.

Because it's not necessary.

However, and more to the point, I think that some may read your statement as implying that a measured resistance <23k&#937; means that bonding is required

It is.

- e.g. (per your measurement to MET) that bonding of the bath would be required if, for example, it were plumbed in copper (almost inevitably with a low resistance to MET).

But, if extraneous, copper tube will be bonded so the value will be very low.

I'm saying that copper pipework is almost inevitably going to have a low resistance to the MET - due to CPCs ,quite apart from bonding. Connect such pipework to a metal bath and the metal bath will have a resistance <<23k to the MET - and your statement could be taken to mean that it therefore needs to be bonded.

I'm still confused about what you are trying to say.

Is it that a bath which is extraneous and bonded by the pipework will read as if it needs bonding?
I.e. all bonded parts will give a reading which requires them to be bonded.