Main protective bonding conductors

[gselectrical]

I have recently carried out maintenance work on some new build properties. Plastic water supply and plastic gas supply entering property. Pipework from water stop tap and gas valve is in copper.

On all the properties there is a 10mm earth conductor from the MET to the water supply and the gas supply. Clamps installed as soon as copper pipework starts.

17th ed consumer unit. All circuits RCD protected and all disconnection times met.

So if you where wiring these properties would you install main protective bonding conductors to these services concidering they are both plastic!?

Cheers

GS

 

[MajorOak]

It may be plastic but the water inside the pipe may eventually come into contact with metal pipe work further up the water network. It also connects to all the other pipework in the house which will now be at earth potential. Earthing the pipes also mean that the potential of the pipes in the house hopefully will not reach 50v (touch voltage) if there is a fault to the pipe as the resistance of the pipe work to earth can increase to 1666ohms before this happens 50/30mA. Bonding the pipes means that this is unlikely to happen

 

[batty]

Is water a good conductor I think not but as metal pipes may induce a potentional it would be a good idea to bond them. There have been a few debates about this before I think you have to use your judgement.

 

[Sidewinder]

Pure water IIRC is actually an insulator, though we don't get pure water through the taps in the UK!

Also AFAIK natural gas is also an insulator, to that can't conduct either.

You could do the "earthy" test, and/or bond, and/or undertake some further reading as IIRC there is "official" guidance out there ESC site perhaps?

You all know what my memory is like!

 

[MajorOak]

You may be talking about pure water, but I would bet the water that comes out of your tap conducts. Tap water conducts electricity because it contains ions. These ions provide a transport system for the flow of electrons.

 

[Sidewinder]

Major,

If you read the post that is what I said! ; ) ; )

 

[batty]

You may be talking about pure water, but I would bet the water that comes out of your tap conducts. Tap water conducts electricity because it contains ions. These ions provide a transport system for the flow of electrons.

We have had a whole thread on this in the past and people even did tests to prove it is not a good conductor try it yourself and see.

 

[Manator]

We have had a whole thread on this in the past and people even did tests to prove it is not a good conductor try it yourself and see.

NO please do not try this experiment. Pure water will NOT conduct electricity, anything you place into pure water to test this must also be pure, or free from contaminants.

 

[MajorOak]

OK so it may not be that good, resistivity of tap water is around 0.1Meg ohm/meter, doh!!

 

[Sidewinder]

Major,

We all live and learn mate!

I have many, many, many a DOH! moment on here and my brain seems at the moment to be in Homer Simpson mode, one thing in and something else falls out the other side!!!

 

[Evans Electric]

As far as I know , its nothing to do with the water in the pipe ( could also be oil) . If there are metallic pipes present in the building , they should be bonded in the usual place . The fact that the feeder pipe is PVC doesn't come into it, nor whether it carries water, oil or gas. AFAIK.

 

[ADS]

Earthing the pipes also mean that the potential of the pipes in the house hopefully will not reach 50v (touch voltage) if there is a fault to the pipe as the resistance of the pipe work to earth can increase to 1666ohms before this happens 50/30mA. Bonding the pipes means that this is unlikely to happen

And if you don't bond the pipes it won't happen at all;\

What do you want to bond next:

Chrome loo holder?

Hanger rail in your wardrobe?

Your key-ring on the coffee table?

If there are metallic pipes present in the building , they should be bonded in the usual place .

Extraneous Conductive Part

A conductive part liable to introduce a potential, generally Earth potential, and not being part of the electrical installation.

If it doesn't fit the description, then it doesn't require 'bonding'.

 

[steptoe]

OK,

may I suggest that perhaps pipework of this nature is intrinsically a part of the fabric of the building almost?

it is in contact with the building at constant points, even passing through the fabric of the building, surely this could warrant it being at earth potential?

no?

isnt this why we dont export TNCS (NOT PME)? difference in potentials?

I think the word here is

"LIABLE"

 

[ADS]

OK,............. in contact with the building at constant points, even passing through the fabric of the building, surely this could warrant it being at earth potential?

If it is at earth potential, then it requires 'bonding' - if not, then it doesn't.

Just because it is a metal pipe within a building does not mean that it requires 'bonding'.

If you were to 'bond' everything that is metal within a building you could actually create more hazards than what were originally there.

 

[steptoe]

yes, I agree with you there ADS,

but main incoming services require bonding unless you can PROVE otherwise,

the oneous is on you to prove they do NOT require bonding.

 

[MajorOak]

If the water pipe feeds a shower or a boiler etc, then the metal work it connects to within the shower or boiler is earthed if you follow that earth back to the MET it then connects to earth electrode at the incoming source if it's a TT or further up stream if it's a PME system or at the sub for a TN-S so the water pipe is introducing an earth potential around the building, be it indirectly.

 

[gselectrical]

And if you don't bond the pipes it won't happen at all;\What do you want to bond next:

Chrome loo holder?

Hanger rail in your wardrobe?

Your key-ring on the coffee table?

Extraneous Conductive Part

A conductive part liable to introduce a potential, generally Earth potential, and not being part of the electrical installation.

If it doesn't fit the description, then it doesn't require 'bonding'.

This is what I thaught. Seems like everybody has different opintions/views on the subject.

If you have a plastic feeder pipe and you are only bonding the internal metal work to ensure it is at 0 potential then would you still bond it 600mm from where it enters the peoperty? Would there be any point!?

During my last assesment, I took my assesor around a new build property. Only service entering property was a plastic water pipe. He asked whether any main protective bonding conductors where present. I said no as the supply was plastic. He said ok thats fine.

Cheers

GS

 

[PC Electrics]

I have recently carried out maintenance work on some new build properties. Plastic water supply and plastic gas supply entering property. Pipework from water stop tap and gas valve is in copper. On all the properties there is a 10mm earth conductor from the MET to the water supply and the gas supply. Clamps installed as soon as copper pipework starts.

17th ed consumer unit. All circuits RCD protected and all disconnection times met.

So if you where wiring these properties would you install main protective bonding conductors to these services concidering they are both plastic!?

Cheers

GS

But they are not plastic are they? You've told us the internal pipework is copper (which it ALWAYS will be for a gas pipe, gas regs) - ergo the [wiring and gas] regs require MPB. What the supply pipe is made of is irrelevant in this situation.

 

[gselectrical]

But they are not plastic are they? You've told us the internal pipework is copper (which it ALWAYS will be for a gas pipe, gas regs) - ergo the [wiring and gas] regs require MPB. What the supply pipe is made of is irrelevant in this situation.

Sorry, I mean the service entering the property is plastic. Therefore not concidered to be an extraneous conductive Part

 

[Doc Hudson]

If the water pipe feeds a shower or a boiler etc, then the metal work it connects to within the shower or boiler is earthed if you follow that earth back to the MET it then connects to earth electrode at the incoming source if it's a TT or further up stream if it's a PME system or at the sub for a TN-S so the water pipe is introducing an earth potential around the building, be it indirectly.

I am not sure paths back through a shower are very common, as very few modern electric showers have many metal parts inside and mixer showers, especially power showers, are often fed at some point by short flexible lengths of pipe for connection to pumps. Most of these I have seen tend to be some sort of composite material not metal. Often plastic push fit.

Doc H.