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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:

    Working on the basis that various posters don't know the difference between bonding and earthing, I would go for bonding the bath. Take a 4mm back to the airing cupboard. Then you will sleep at night. If you take any notice of the 18th guide book you won't bond anything. (Although it's been saying bond everything for 50 years) 




    Are you one of those DNO guys refusing to connect new electricity supplies to houses back in the 1980’s because the metal waste fitting mounted in the plastic bath to connect it to the plastic waste pipe didn’t have a green and yellow wire connected to it?


    How far are you going to go when it comes to installing equipotential bonding in bath and shower rooms? I was in a new house in the 1980’s when the connection of a new supply was refused, because the plastic shower tray had a metal waste connected to a plastic waste pipe that was not bonded.


    Andy B

  • 0

    UKPN:

    Working on the basis that various posters don't know the difference between bonding and earthing, I would go for bonding the bath. Take a 4mm back to the airing cupboard. Then you will sleep at night. If you take any notice of the 18th guide book you won't bond anything. (Although it's been saying bond everything for 50 years) 



    Pretending for the moment that the bath is an extraneous CP, that'll be bare copper will it? 544.2.3
  • 0
    Just out of interest,  what happens in the airing cupboard?


    Andy B
  • 0

    UKPN:

    Working on the basis that various posters don't know the difference between bonding and earthing, I would go for bonding the bath. Take a 4mm back to the airing cupboard. Then you will sleep at night. If you take any notice of the 18th guide book you won't bond anything. (Although it's been saying bond everything for 50 years) 



    Dangerous nonsense from one who obviously does not know the difference between bonding and earthing.


     
     

  • 0

    UKPN:

     (Although it's been saying bond everything for 50 years) 




     

    No it hasn't.


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    The old bath was bonded back to the terminal block by main consumer unit over 6mm earth cable via the airing cupboard.



    There might have been a sensible reason why it was done like that originally. Back in the old days (when internal plastic water supply pipes and push fit fittings were unknown) it wasn't unknown to see (main) bonding carried out at some random point on the plumbing system rather than necessarily at the intake position - I've seen it done in the airing cupboard - simply because the immersion circuit was being renewed so it was easiest to run the G/Y alongside the T&E. As both taps were likely had good continuity with a metal bath, bonding the bath was a convenient way to bond all the pipework in one go. Likewise in the past the difference between main and supplementary bonding wasn't as clear as it is today (and no omission of bathroom bonding because everything's 30mA RCD protected back then either) - if bonding the pipework was at all difficult, bonding the bath would be just as effective (or often done as well, although not at all necessary). Such odd (to modern eyes) bonds where often left in place when "proper" main bonding was installed to the intake positions, so the whole things starts to look very odd and messy in time.


    I agree though - if the new bath has no metallic connections to anything else - it's far better left unbonded.


      - Andy.
  • 0
    Contrary to common belief supplementary protective equipotential bonding is still required in bathrooms, see Regulation 7091.415.2. 


    However it may be omitted IF where all 3 of the conditions set out in 701.415.2 are met. And where necessary a test has been carried out to prove compliance with 415.2.2.


    The big question is can you omit the supplementary bonding in the "location" (the bathroom) if there is no main bonding as it is not required?
  • 0
    The shower manufacturer may have installed a supplementary bonding connection within the electric shower casing, it depends on which manufacturer it is. Alternatively the electrician may have added one if appropriate, but either way there isn’t likely to be any exposed conductive parts to the shower that the user of the shower can touch.


    The only part of the installation that is described in the original post that is likely to have a voltage on it is the wall mounted taps. If they are mono block taps you aren’t going to put a hand on the hot tap and the other on the cold tap and be exposed to a voltage difference between them.


    But there hasn’t been any mention of a radiator, can you reach that to get a towel off it whilst you are still turning a tap off?


    The bath as described is unlikely to present a risk, but there still could be other risks present.


    Andy Betteridge
  • 0
    The assumption is there is a radiator present, which would be bonded together with the bath and any other metalwork. But we know that don't we, its been in the regs for 50 years. 

    Regards, UKPN. 

  • 0

    The assumption is there is a radiator present, which would be bonded together with the bath and any other metalwork. But we know that don't we, its been in the regs for 50 years. 



    No, not any metalwork - only exposed-conductive-parts and extraneous-conductive-parts - it's been specified like that at least as far back as the 15th Ed. A bath with no metallic pipe connections isn't likely to be an extraneous-conductive-part, neither indeed is simple radiator if it's fed with reasonable lengths of plastic pipe (despite any rust and inhibitor in the heating water).


       - Andy.

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