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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
  • 0

    John Peckham:

    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?




    "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?"


    That`s the question I`ve asked more than a couple of times and everyone thinks I`m stark raving mad (That aside I am stark raving mad but the question still stans)

  • 0
    Main bonding is always reqd with PME. Wiring regulations (non mandatory) bonding is different, it doesn't allow for voltage rises on the supply. This is why bathrooms are "an area of special risk" and supplementary bonding is reqd.

    Regards, UKPN.
  • 0
    In a new house with all plastic pipework, do you put the pipe earth clamp onto the white plastic pipe or the blue plastic pipework?
  • 0

    Sparkingchip:

    In a new house with all plastic pipework, do you put the pipe earth clamp onto the white plastic pipe or the blue plastic pipework?




    Both, and make sure that you include the yellow pipe too. ?

  • 0
    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.
  • 0
    New gas supply pipes are now plastic up to the meter, pipe jointers stopped threading pipe many years ago and now fusion weld the plastic pipework.
    https://www.pipestock.com/gas/mdpe/mdpe-pipe-coils


    And no, I have never seen a new plastic water main electrically bonded just in case it is changed to copper.


    I am surprised that you are surprised!


     Andy Betteridge
  • 0
    It would appear that UKPN perfectly illustrates my post of yesterday, 26th at 4.56pm.


  • 0
    "people used to do that (including things like window frames) and a myth has come about that the 15th required bonding everything"


    They did. It was standard practice in the 70s and 80s to Equipotentially Bond the Crittle window frames that were fitted in prefabricated houses as the supporting studding was fixed into the ground floor and the ceiling.


    Legh
  • 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
  • 0

    Legh Richardson:
    "people used to do that (including things like window frames) and a myth has come about that the 15th required bonding everything"


    They did. It was standard practice in the 70s and 80s to Equipotentially Bond the Crittle window frames that were fitted in prefabricated houses as the supporting studding was fixed into the ground floor and the ceiling.




    Oh my word! I must run some green and yellow up to the 1920s Crittall windows in my conservatory. Oh yes, and I mustn't forget to bond the steel framework, which being buried in the floor, might well be an extraneous CP. It will complement the 1980s SRCDs. ?

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