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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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  • 0
    Back in the 1980’s I saw some public toilets in Wales and a show house built by a developer in Herefordshire that had the lead flashing and roof lights connected to the equipotential bonding.


    It all got a bit out of hand to say the least, I was in a house being built on the Cotswolds and the DNO guy was explaining that there had to be a copper mat in the fibreglass shower tray connected to the equipotential bonding in the shower room.


    In the majority of houses it used to be that the basin and bath had two separate taps, the cold was connected directly to a buried metal water supply pipe at earth potential, the hot could have been off a cylinder fed through a plastic tank in the loft with the only earth connection through the circuit protective conductor of the immersion heater leaving the risk that the hot tap and it’s pipework could have voltage on it if there was an insulation fault on the cables or immersion heater. If you put a hand on each of the taps at the same tim you could be in serious trouble. Actually I still see a lot of places like that and find myself installing supplementary equipotential potential bonding every so often.


    But mono block taps, plastic pipes, non-metallic baths and shower trays all start to remove the risks.


    Andy Betteridge
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  • 0
    Back in the 1980’s I saw some public toilets in Wales and a show house built by a developer in Herefordshire that had the lead flashing and roof lights connected to the equipotential bonding.


    It all got a bit out of hand to say the least, I was in a house being built on the Cotswolds and the DNO guy was explaining that there had to be a copper mat in the fibreglass shower tray connected to the equipotential bonding in the shower room.


    In the majority of houses it used to be that the basin and bath had two separate taps, the cold was connected directly to a buried metal water supply pipe at earth potential, the hot could have been off a cylinder fed through a plastic tank in the loft with the only earth connection through the circuit protective conductor of the immersion heater leaving the risk that the hot tap and it’s pipework could have voltage on it if there was an insulation fault on the cables or immersion heater. If you put a hand on each of the taps at the same tim you could be in serious trouble. Actually I still see a lot of places like that and find myself installing supplementary equipotential potential bonding every so often.


    But mono block taps, plastic pipes, non-metallic baths and shower trays all start to remove the risks.


    Andy Betteridge
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