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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
Parents
  • 0
    The one to watch for is the external cast iron soil pipe - do you want it dangerous in the back yard and safe in the bathroom, or the reverse. I am pretty sure the only time I ever bonded one was when the pipe between bath and stack was in 1.75" copper.

    I'm not sure you need 0.4 second ADS for the failing immersion, you certainly did not under previous regs, 5secs would have been considered enough. Hopefully the CPC of the immersion supply serves to pop the fuse in a sensible time., I suspect that  adding the lighting CPC in parallel with it, and bonds to a selection of metal parts, does not appreciably alter the breaking time, unless those parts have an additional and  lower resistance path back to earth. We do ourselves no favours with our tendency to use reduced CPCs in twin and earth, as the on-fault voltage is more like 2/3 than 1/2 of the supply.

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  • 0
    The one to watch for is the external cast iron soil pipe - do you want it dangerous in the back yard and safe in the bathroom, or the reverse. I am pretty sure the only time I ever bonded one was when the pipe between bath and stack was in 1.75" copper.

    I'm not sure you need 0.4 second ADS for the failing immersion, you certainly did not under previous regs, 5secs would have been considered enough. Hopefully the CPC of the immersion supply serves to pop the fuse in a sensible time., I suspect that  adding the lighting CPC in parallel with it, and bonds to a selection of metal parts, does not appreciably alter the breaking time, unless those parts have an additional and  lower resistance path back to earth. We do ourselves no favours with our tendency to use reduced CPCs in twin and earth, as the on-fault voltage is more like 2/3 than 1/2 of the supply.

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