Earth bonding

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I've read a bit about earthing on the forum and it has been very helpful - it is one area the DIY books are poor on. I would be grateful if someone could clarify a few points:

I live in a block of flats and none of my pipework etc is cross bonded. I assume (?) that the main gas and water pipes supplying all of the flats are earthed where they enter the building (about 80 feet from my flat). Do I need to attach earth clamps to them where they enter my flat and link them back to the CU?

Which brings me to my next point - linking anything back to the CU is hard work (at least trying to do it neatly) because the floors are concrete and all cabling is run in the half inch space above the plasterboard ceiling. I have managed to lead a 10mm earth wire from the CU across into the void space where all of the service ducting, pipework etc is located. I put a 4-way earthing connector block on the end of this 10mm cable and used it to supply an earth to the new light fitting I put up in the bathroom. (I know the lighting circuit should have an earth but the cabling seems to be in good condition [it is 1960s] and given the problem feeding cables a total rewire of the lighting circuit would be a pretty big job). Can all of my bathroom and kitchen cross bonding be linked back to this 4-way connector block, and thus back to the CU through the one 10mm cable?

In the kitchen I was planning to cross bond the sink, cold and hot pipes (what about the gas pipe?) and link them back to the earth block in the void. Does it matter where I attach the earth clamps to the pipes, ie under the kitchen sink or about 2 feet from the sink on the other side of the wall in the void space? This is pretty much the point at which the cold and gas pipes enter the flat.

In the bathroom, I was planning to connect together all cold and hot pipes supplying toilet, sink, bath, shower, and earth the bath itself and then connect these back to the 4-way earth block. All of these pipes to toilet sink etc come through the wall from the void - can I put the earth clamps on the pipes on the void side of the wall (neater looking job), or do they all have to be on the bathroom side of the wall (there would only be about 6 inches difference).

[Incidently, looking at pictures of equipotential bonding in bathrooms in books, although the toilet, sink and bath are all fed off one cold water pipe via T pieces, the piece of pipework leading to each of them has its own earth connection - why can't you just earth the pipe once? Is it because you can't assume that the solder/compression fittings used to T off the main pipe will provide a low resistance path? ]

Am I ok using 4mm for all of this (I have seen some say 6mm)? Does it definitely have to be an unbroken length of cable with the earth clamps threaded on where in the insulation is stripped off?

Lastly (sorry, I've gone on a bit!) do I need to include the earths to the shaver socket and shower in the equipotential bonding? If so, physically how do I loop them into this unbroken length of 4mm cable? Even if I break into the cable, I just don't think there would be enough space in the screw terminals to take the cable already supplying the shower/shaver AND two more 4mm cables/one doubled over cable.
 
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jss said:
I've read a bit about earthing on the forum and it has been very helpful - it is one area the DIY books are poor on. I would be grateful if someone could clarify a few points:

I live in a block of flats and none of my pipework etc is cross bonded. I assume (?) that the main gas and water pipes supplying all of the flats are earthed where they enter the building (about 80 feet from my flat). Do I need to attach earth clamps to them where they enter my flat and link them back to the CU?
That would be a very good idea.

Which brings me to my next point - linking anything back to the CU is hard work (at least trying to do it neatly) because the floors are concrete and all cabling is run in the half inch space above the plasterboard ceiling. I have managed to lead a 10mm earth wire from the CU across into the void space where all of the service ducting, pipework etc is located. I put a 4-way earthing connector block on the end of this 10mm cable and used it to supply an earth to the new light fitting I put up in the bathroom. (I know the lighting circuit should have an earth but the cabling seems to be in good condition [it is 1960s] and given the problem feeding cables a total rewire of the lighting circuit would be a pretty big job). Can all of my bathroom and kitchen cross bonding be linked back to this 4-way connector block, and thus back to the CU through the one 10mm cable?
16mm would be better, but I understand the problems you face, and 10mm is certainly better than 0mm! It should run back to the earth connection of your supply - i.e. directly to what the CU earth connects to, not the CU itself.

In the kitchen I was planning to cross bond the sink, cold and hot pipes (what about the gas pipe?) and link them back to the earth block in the void. Does it matter where I attach the earth clamps to the pipes, ie under the kitchen sink or about 2 feet from the sink on the other side of the wall in the void space? This is pretty much the point at which the cold and gas pipes enter the flat.
The incoming services should be bonded as close as possible to where they enter

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There's no requirement for supplementary bonding in the kitchen itself, but IMHO it's a good idea to do the sink.

In the bathroom, I was planning to connect together all cold and hot pipes supplying toilet, sink, bath, shower, and earth the bath itself and then connect these back to the 4-way earth block. All of these pipes to toilet sink etc come through the wall from the void - can I put the earth clamps on the pipes on the void side of the wall (neater looking job), or do they all have to be on the bathroom side of the wall (there would only be about 6 inches difference).
6" away should be fine - don't forget though that all bonding connections should be accessible.

[Incidently, looking at pictures of equipotential bonding in bathrooms in books, although the toilet, sink and bath are all fed off one cold water pipe via T pieces, the piece of pipework leading to each of them has its own earth connection - why can't you just earth the pipe once? Is it because you can't assume that the solder/compression fittings used to T off the main pipe will provide a low resistance path? ]
Yup

Am I ok using 4mm for all of this (I have seen some say 6mm)? Does it definitely have to be an unbroken length of cable with the earth clamps threaded on where in the insulation is stripped off?
4mm will be fine - covers most possibilities for the size of the CPCs in the bathroom. See http://www.tlc-direct.co.uk/Book/5.4.3.htm for the table of sizes. It does not have to be unbroken - only the main bonding cables need to be unbroken. Supplementary bonding just wires everything together locally.

Lastly (sorry, I've gone on a bit!) do I need to include the earths to the shaver socket and shower in the equipotential bonding? If so, physically how do I loop them into this unbroken length of 4mm cable? Even if I break into the cable, I just don't think there would be enough space in the screw terminals to take the cable already supplying the shower/shaver AND two more 4mm cables/one doubled over cable.
Yes you do - that is the whole point of supplementary bonding. This doc http://www.iee.org/Publish/WireRegs/EarthingPlasticPipes.pdf, although it is about what do do when you have plastic pipes also has useful diagrams of metal-piped bathrooms.
 
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Thanks - that's really useful

6" away should be fine - don't forget though that all bonding connections should be accessible.

The void is big enough to stand up in and is accessed through a removable panel, so that should be OK. If I lived in London I think it would be called a compact and bijou bedroom. With a 12 inch soil pipe running straight through the middle of it..... ;)

The two web links are really good.

Thanks for taking the time to respond.
 
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Thanks - that's really useful

6" away should be fine - don't forget though that all bonding connections should be accessible.

The void is big enough to stand up in and is accessed through a removable panel, so that should be OK. If I lived in London I think it would be called a compact and bijou bedroom. With a 12 inch soil pipe running straight through the middle of it..... ;)

The two web links are really good.

Thanks for taking the time to respond.
 
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Question - does anybody know if that void, given that it's in a block of flats, might require the use of LSZH (or LS0H if you prefer) cables re fire regulations?

I do fret, sometimes....
 
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Supplementary bonding.

Route of earth cable

I intend to upgrade supplemenatry bonding in bathroom. Pipes are no problem but downflow heater, towel rail and shaver socket are on 3 different walls. The downflow heater is installed at over 6 foot high and the shaver socket is about 4 foot.

I know that I bond from the cpc to pipework for electrical equipment but I will have to chase down walls in order do this.

Does this earth wire have to be mechanically protected in some way as the path will not be obvious/follow IEE regs for live main cable. No one is going to be immediately harmed if this wire is breached in some way but the whole purpose of the protection would be lost.

If not mechanically protected -
connections have to be accessible but can I route cable behind skirting board/architrave :?:

Can I wire from one cpc to another then wire to pipework :?:

Do I include lighting circuit in this if it is over 2.5 metres high :?:

I have some 10mm earthing cable - there is a minimum size for various cables and 10mm may be over the top, but is it ok to use :?:

appreciate any comments
 

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