Earth Bonding

[EddieB]

Yes, I know its a much discussed issue, but I would be obliged if someone could explain to me why a copper water pipe entering the building which has a metal stopcock fitted 2 inches above the floor level which is located under the kickboard of a kitchen unit with the outgoing pipework in plastic have to be bonded. I know because the regulations say that it must but what the rationale behind it ?

 

[littlespark]

When you say “outgoing” does that mean inside the building, or going outside?

Edit. I see you say it’s copper entering the building.

It’s all down to extraneous conductive parts… and not limited to water pipes.

any large lump of metal that is in contact with the mass of earth needs to be bonded. It’s just to ensure there is zero potential between one lump of metal and another.

 

[westward10]

The metal pipework is at earth potential and unless it is connected to other exposed conductive and extraneous parts then it's potential is different.

 

[Spoon]

I think the OP is referring to, all the exposed conductive and extraneous parts are under the kickboard, and very hard to get in contact with... The risk would seem low...

 

[EddieB]

When you say “outgoing” does that mean inside the building, or going outside?

Edit. I see you say it’s copper entering the building.

It’s all down to extraneous conductive parts… and not limited to water pipes.

any large lump of metal that is in contact with the mass of earth needs to be bonded. It’s just to ensure there is zero potential between one lump of metal and another.

Thanks for your response
I'm specifically asking about the water pipe entering the building when it immediately converts to plastic, I'm aware of the need of equipotential bonding and the need for it but in the scenario above why does it require it

 

[EddieB]

The metal pipework is at earth potential and unless it is connected to other exposed conductive and extraneous parts then it's potential is different.

Thanks for your response, but how given the scenario I've described is that pertinent as its never going to be in contact with any other part of the installation.

 

[brianmoooore]

A human with two arms may be in contact with the stopcock and an earthed part of the installation at the same time.

 

[EddieB]

A human with two arms may be in contact with the stopcock and an earthed part of the installation at the same time.

Thanks for your response, no human I've ever heard of or seen could, however I will accept that if they have an Orangutan in the house it may be possible

 

[brianmoooore]

Doesn't have to be for when the kitchen is in place. Kitchen could be being refurbished with all sorts of electrical tools around with earthed metal cases. Even things like fuses and RCDs aren't needed when things are working correctly. We design for when things go wrong, not when all is well