Earthing water. Part plastic, part copper

[robsparx]

On the job I'm at, there is a plastic incoming water main, with a plastic pipe taken from it on the consumer side. The plastic runs up into a bathroom and copper pipe is taken off it to supply the bathroom. The plastic pipe carries on up into the loft which i then assume feeds more copper pipework.

As I see it, there is no requirement for supplementary bonding, as the copper is supplied by plastic. But there would be a requirement to earth any copper installation if it is introducing earth potential.

Would that mean I would have to seperately earth every piece of copper installation that is teed off the plastic. Not had too much experiences with plastic pipes before.

 

[bugsy]

There is no requirement to main bond an incomming plastic service providing the pipe work within the installation is plastic, however where the installation contains metal pipework main bonding is recommended unless you can confirm and metal pipework within the building does not introduce an earth potential.
Judging by by your discription of the installation this would not be the case , are both services plastic?

 

[robsparx]

Gas is metal, already bonded as its in the garage with the CU.

So if I've got 0v from live to any of the copper pipework then I don't need to bond anything?

 

[pushrod]

Gas is metal, already bonded as its in the garage with the CU.

So if I've got 0v from live to any of the copper pipework then I don't need to bond anything?

Think that would mean that all your copperwork was already live

edit : what you are looking for is insulation resistance readings of greater than 23kΩ between your MET and suspect pipe work to see if it is an extraneous-conductive-part

 

[bugsy]

Have you cross bonded anything?

 

[robsparx]

No, not installed any bonds

 

[bugsy]

As pushrod say's test it, if the gas supply feeds boiler and that connects to copper pipe work you may introduce fault path

 

[Astro800]

The copper pipe is not an Extraneous Conductive Part & only requires earthing if cables are run within 25mm. To cover yourself, do a test. I presume that all the power circuits are protected by a 30mA RCD?

Personally, I would bond all the copper pipe in the bathroom anyway. Better to be safe than sorry.

 

[Deleted member 9648]

The copper pipe is not an Extraneous Conductive Part & only requires earthing if cables are run within 25mm. To cover yourself, do a test. I presume that all the power circuits are protected by a 30mA RCD?

Personally, I would bond all the copper pipe in the bathroom anyway. Better to be safe than sorry.

Where does it say this?.....new one on me.

 

[Astro800]

Somewhere in the new Regs, don't ask me to find it again, I don't have a copy here. I thought that to be a strange one too. The Regulation was pointed out to me. It's one of those swines to find. If they made the Regulations easier to use (like the handbook), it would cause less confusion. I have always thought it was a mess since the 15th Edition. Lets face it, the 15th was a right cockup!

 

[Guest111]

I was always told that if you had for example a copper water pipe which had been cut and a section of plastic inserted,or a plastic fitting then you should place a clamp either side of plastic and link with a suitable size piece of earth cable, to maintain earth continuity of pipe.

 

[rich.250]

Test from your MET to the pipe/ pipes in question. If it is greater than 23K ohms It is deemed electrically separate from earth. And does not require bonding, if less it does to bring it to the same potential to reduce the risk of touch voltages.
It is only required to bond at source any possible parallel path.
Supplementary bonding may be required if no 30mA rcd protection

 

[Astro800]

I was always told that if you had for example a copper water pipe which had been cut and a section of plastic inserted,or a plastic fitting then you should place a clamp either side of plastic and link with a suitable size piece of earth cable, to maintain earth continuity of pipe.

I always used to do the same, but if it's PVC coming in & the copper in the middle is not an Extraneous Conductive Part, ie: no earth potential & it doesn't run next to cables within 25mm. It doesn't require earthing apparently. You could just bond it to the other water pipes anyway if it worries you.

 

[Deleted member 9648]

I was always told that if you had for example a copper water pipe which had been cut and a section of plastic inserted,or a plastic fitting then you should place a clamp either side of plastic and link with a suitable size piece of earth cable, to maintain earth continuity of pipe.

Generally pointless......bonding is required at the point of entry of an extraneous CP to the location,by doing it there the hazard has been dealt with,it doesnt matter beyond that point.

 

[Astro800]

Generally pointless I know, I was being ironic. We could always go back to earthing every sodding thing on the outside of a house. Windows, window cleaners ladders, hanging baskets, van on your drive, dog, cats etc. An electricians life was such fun.

I remember having to earth PVC water pipes on building sites in Birmingham. I bet those earth straps are still there now. There is no accounting for stupidity. PVC water pipes had just come out & in the regs it said pipework had to be earthed. The arguments & moaning from the lads stopped when we were told "you don't need to earth those water pipes any more". We told the site managers that from the beginning. This story has been repeated many times, other electricians have told me the same thing too.