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Bonding a metal bath

David-Adams
Good evening


I am having one of those moments where I can’t sleep because I am worrying about something I probably don’t need to. That’s the rational part of me talking, unfortunately the anxiety monster won’t b***** off. 


We have just had our old cast iron bath replaced with a nice new shiny steel one. The old bath was bonded back to the terminal block by main consumer unit over 6mm earth cable via the airing cupboard. We also have an electric shower. 


The new bath has no taps on it (they are wall-mounted and fed by copper pipes). The waste is all plastic. The electric shower has been replaced with a new electric shower. The copper pipes in the airing cupboard have been connected via a new 4mm earth cable. My electrician says that according to the 18th edition, there is no requirement for the metal bath to be bonded. 


I have no reason to doubt him, except for the anxiety monster eating away at my brain I mentioned earlier. What limited literature I have found seems to suggest this is correct, but in some circles it is a hotly debated topic with contradicting views. I was just wondering if someone could confirm this for me please. I would also be interested in understanding why this is the case to satisfy my own natural curiosity of all things!


Many thanks in advance
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    UKPN:

    Yes indeed, the method is widely used, not on gas pipes of course they are steel and bonded as a matter of course. The plastic water service, after the stop cock, normally grey throughout the property has a clip and 10mm green yellow at the point of entry so that in the future if the service is changed to copper the bond/clip will be there ready. I am surprised you haven't seen it done. 

    Regards, UKPN. 




     

    Metallic pipes entering the building having an insulating section at their point of entry need not be connected to the protective equipotential bonding (Regulation 411.3.1.2).

    https://electrical.theiet.org/bs-7671/18th-edition-changes/


    So so long as there is a reasonable length of plastic pipe between any metal water pipe inside the property and a buried metal water pipe at the point of entry into the building there isn’t any need to install a main protective bond.


    So if someone did decide to replace sections of plastic pipe with shiny chrome plated pipe for aesthetic reasons, so long as a insulating plastic pipe remains in place it doesn’t matter whether the buried service pipe is plastic or metal, either way it doesn’t need a main protective bond.


    Therefore the idea that a main protective bond should be installed to plastic pipework just in case it is changed to copper is really a non-starter even if the buried service pipe is metal.


    Andy Betteridge 


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  • 0

    UKPN:

    Yes indeed, the method is widely used, not on gas pipes of course they are steel and bonded as a matter of course. The plastic water service, after the stop cock, normally grey throughout the property has a clip and 10mm green yellow at the point of entry so that in the future if the service is changed to copper the bond/clip will be there ready. I am surprised you haven't seen it done. 

    Regards, UKPN. 




     

    Metallic pipes entering the building having an insulating section at their point of entry need not be connected to the protective equipotential bonding (Regulation 411.3.1.2).

    https://electrical.theiet.org/bs-7671/18th-edition-changes/


    So so long as there is a reasonable length of plastic pipe between any metal water pipe inside the property and a buried metal water pipe at the point of entry into the building there isn’t any need to install a main protective bond.


    So if someone did decide to replace sections of plastic pipe with shiny chrome plated pipe for aesthetic reasons, so long as a insulating plastic pipe remains in place it doesn’t matter whether the buried service pipe is plastic or metal, either way it doesn’t need a main protective bond.


    Therefore the idea that a main protective bond should be installed to plastic pipework just in case it is changed to copper is really a non-starter even if the buried service pipe is metal.


    Andy Betteridge 


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