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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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    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.
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  • 0

    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.
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