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Earthing plastic/ PVC Pipes and mixture of Metal Pipes

Discussion in 'Electrics UK' started by Mikefromlondon, 19 Apr 2021.

  1. Mikefromlondon

    Mikefromlondon

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    In a property where the incoming water mains is supplied via a PVC pipe, and is not bonded to earth but in sections after the stop cock, some of the plumbing has been carried out in copper 15mm pipes, using plastic to metal adaptors, so the question is since water itself is not a very good conductor of electricity so do any copper pipes in between or connected to kitchen sink, bath sink etc need seperate earth bonding as properties once required bonding all pipes work connected to kitchen, bath taps and bath tub itself required earth bonding but later on this requirement was deemed unnecessary . Please let me have your comments if this bonding is necessary where incoming water supply is in plastic pipes. Of course I don't mean bonding plastic pipe itself but any copper pipes that connect to it afterwards.
     
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  3. EFLImpudence

    EFLImpudence

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    If the incoming supply is plastic, then main bonding is not required - not possible.

    Supplementary bonding is not required in kitchens. It might be required in a bathroom depending on various things.
     
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  4. Mikefromlondon

    Mikefromlondon

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    Thanks mate, much obliged. (I was obviously referring to metal pipe sections if they would need earthing)
     
  5. EFLImpudence

    EFLImpudence

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    They do not require 'bonding' because they are not 'earthed' by the ground.
     
  6. JohnW2

    JohnW2

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    Yes, but the most important of those various things is that there have to be some extraneous-c-ps to bond - otherwise bonding is impossible, regardless of any 'other things'. If the supply to the property is in plastic, and provided the bathroom has no metal waste pipes, it seems very unlikley that there would be anything extraneous ('liable to introduce a potential' into the bathroom) to bond.

    Kind Regards, John
     
  7. EFLImpudence

    EFLImpudence

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    :)

    Well, Yes, obviously. Not possible to bond what is not there.

    If you are just referring to main bonding then - of course. I did say main bonding is not required.

    However that does not automatically rule out there being extraneous-c-ps to the bathroom and supplementary bonding being required - depending on various things.
     
  8. JohnW2

    JohnW2

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    Exactly.
    I thought I was pretty clear in talking explicitly about supplementary bonding (in response to your comment about SB) when I wrote what I did about it being very unlikley that there would be any conductors which were 'extraneous' to the bathroom ...
    Is it not the case that that 'extraneous to the bathroom' means "liable to introduce into the bathroom a potential other than the potential of the property's equipotential zone "

    Mind you, I may well be missing something, since I've always wondered how anything entering a bathroom could (assuming all required main bonding was present could ever "introduce into the bathroom a potential other than the potential of the property's equipotential zone ".

    Kind Regards, John
     
  9. Mikefromlondon

    Mikefromlondon

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    Ok here is why I asked this question and my concern, suppose and yes it is based on an unlikely occurrence, but such incidents can happen even if the odds are against it.
    Say the incoming service pipe is plastic and cannot be bonded to earth, and at some point after the stop cock the rest of the pipework has been carried out in copper 15mm pipe work, this is actually a case in one property where I have engaged an Electrician to carry out safety checks and issue an EICR. and I was wondering if this earth bonding impedance would be raised by the Electrician if he tested earth resistance of pipework to main earth bonding.

    So suppose somewhere in the property one of the copper pipes comes into contact with a live conductor, and since it is not bonded to a solid earth, so the whole pipework becomes live with water conducting some of the current through it into the ground at source of water, how many mili amps or amps would depend on the diameter of the water pipe and its conductivity (resistance)

    Could then an occupant of the house possibly get electrocuted if he or she touched any of the pipework, for instant touching a kitchen tap and at the same time manages to touch nearest electrical appliance that was properly earthed, such as a fridge, washing machine, an electric cooker etc etc.

    So my view or opinion was that if perhaps any part of the water supply uses metal pipe it should be electrically bonded to an earth. This would remove the possibility of a live conductor accidental, or unintentionally making the metal part of the pipe work at live potential, unless the water in the plastic pipe was able to carry sufficient current to knock out the RCD where fitted and where in older installations it may not pass sufficient current to blow out a fuse or MCB.

    ( The property concerned has RCD fitted on its power circuit but not on its lighting circuit, and this is one reason lighting circuit should also be protected by a seperate RCD or use of RCBO to offer better protection)
     
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  11. EFLImpudence

    EFLImpudence

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    Ok.

    No. That would be main bonding if required because of for example a metal waste pipe, wouldn't it?
    It is whether it is an extraneous-c-p (or exposed-c-p) to the more stringent equipotential zone of the bathroom which has to be limited by supplementary bonding to 50V in the event of a fault.

    I might be missing something as well as I'm not sure why you are asking this after all this time.

    Have you discovered something which has made unnecessary what we have been doing for ever?
     
  12. Mikefromlondon

    Mikefromlondon

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    I am not sure if your comments are directed at me, the plastic water incoming service pipe enters the property through ground straight into the utility room which is at the back of the house towards the rear garden, furthest away from the front of the house where the equipotential bonding is. It is TN-S based earthing, in a dedicated cupboard outside the premises, which also houses the gas meter and pipework, but no water piping, the gas meter is earthed as required within 600mm from its outlet, however the plastic water pipe enters from below ground into the utility room through its concrete floor, and rises to about a foot and has a stop cock, from then on it is plumbed in a mixture of metal and plastic pipes, in other words over a period of time, some of the plastic pipework was replaced by copper pipe by a plumber who installed a new central heating and he also plumber the kitchen in copper pipework, but left the upstairs pipework into the bathroom in plastic pipes.

    So the bathroom is in plastic, whilst the kitchen next to utility room is in copper. The metal part of the pipe work is not bonded electrically via an earth conductor to Equipotential bonding, but I forgot it may well be earthed through gas pipework through the Combi boiler as it has copper gas feed and is also connected to water supply via the copper pipes, so I suppose the copper pipework would be earthed through the boiler chassis, but has no seperate earth bonding, so i was wondering if this would fail the EICR.

    I was wondering if I may be asked to run a dedicated earthing bond from copper pipes to equipotential bonding some 10 meters away from the point it becomes copper in the utility room at the back of the house to the front of the house and using I suppose 10mm earthing bond wire??!!!
     
    Last edited: 20 Apr 2021
  13. JohnW2

    JohnW2

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    In theory, that could happen - but, the same is true of anything metal within the house (window frames, filing & other cabinets etc. etc.).

    What you are talking about is, technically speaking, 'earthing' rather than 'bonding', since it's purpose is to cause a fuse to blow, or a breaker to trip, (and thereby disconnect the electricity) if a live conductor comes in contact with the 'earthed' item - whereas the purpose of 'bonding' is to minimise differences in potential between any two simultaneously touchable things, without necessarily causing any protective device to operate.
    One thing you perhaps need to consider is that there is a 'downside' (which is a sort-of corollary of the scenario you describe above) to earthing things that are not already earthed. Consider a situation in which a person comes into contact with a live conductor, or something which has become live - maybe due to a frayed/damaged cable on a vacuum cleaner, a faulty hairdryer/whatever, or whatever else. If they simultaneously touch an earthed tap, pipe, radiator or whatever, they will get an electric shock, but if that tap/pipe/whatever had not been earthed, they would not have got a shock. It's therefore not quite as simple a decision as you suggest, because by reducing/eliminating the risk of electric shocks in one scenario, you are also increasing the risk of shocks in other scenarios.

    Returning to the scenario you described, in practice, even when the incoming water supply is in plastic, if most/all of the internal pipework is copper, then most, if not all, of that pipework will be 'earthed' by things it is connected to. Certainly anything to do with central heating or hot water (pipes, radiators, taps etc.) will be earthed, since the pipework will be in electrical continuity with boiler, pumps, motorised valves, immersion heathers etc., all of which will be earthed, and will earth the connected pipework. Even cold water pipes and taps will usually be 'incidentally earthed' - e.g. by being in electrical continuity with the HW pipes at mixer taps, by hot and cold taps being attached to the same metal sink etc.

    Kind Regards, John
     
  14. JohnW2

    JohnW2

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    Just a 'holding reply' (things I hate receiving)! ....

    You ask some interesting and valid questions. I am currently thinking as deeply as I can about some uncertainties and 'cans of worms' in my mind, and will attempt to respond soon if/when my thinking achieves anything - hopefully tomorrow!

    Kind Regards, John
     
  15. Mikefromlondon

    Mikefromlondon

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    Update, the Electrician did all his checks, using his apparatus, and conducted visual observations, took out a few sockets randomly to examine inside, etc, checked the CU, and was satisfied with almost everything until he came to the utility room where the boiler and most of the copper pipework is, he suggested that i bond all pipes work together with 10mm earth wire, I had already changed the bath light to IP44, and replaced 6mm earth wire with 10mm to the gas meter outlet pipe, so all went Ok, luckily I had some earthing clamps and a length of 10mm earth wire, so I quickly bonded 5 clamps to pipes under the boiler and he was satisfied and issued an ECIR report .
     
  16. SUNRAY

    SUNRAY

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    Something which I always feel is totally unnecessary and usually quite ugly.
     
  17. JohnW2

    JohnW2

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    There would actually have been no justification for him not to issue a ('clean') EICR even if you hadn't added those bonds - which, aside from any discussions, are definitely not required by the regulations in relation to which his EICR inspection is meant to be based.

    Anyway, I'm glad you've got your EICR!

    Kind Regards.
     
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