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bonding a short section of water supply pipe

wallywombat
In a victorian terrace house, a lead water supply pipe enters the damp cellar, runs about a meter along the wall to the main brass stopcock, then converts to plastic pipe before exiting the cellar to the rest of the house (which is likely to be a mixture of copper and plastic). The stopcock is a couple of feet away from the CU. Should the supply pipe be bonded? My feeling is no, but I'd be interested in other opinions.


While I'm on the subject, a more general question. Why must any bonding be done after the main stopcock? For example where the supply tees off immediately after the stopcock, is it better to bond one of the tees, or bond just before the stopcock? Where there is a long run of supply pipe before the stopcock, is it better to bond after, with a long MPBC run back to the MET, or bond it near the MET even where that's before the stopcock?
  • 0
    A nice big diverted neutral current could cause a house explosion

    So what do you think happens with the lead sheath of old PILC service cables - which have a substantially smaller c.s.a. than a lead water pipe?


      - Andy.
  • 0
    Ridiculous! Copper is softer than Lead Z, particularly if recently annealed. So I assume you don't bond copper pipes either, particularly as they are much thinner walled? The diverted N current to melt a 1" gas pipe would need to be several hundred Amps to melt it!
  • 0
     I reckon the reference in the regulations to hard pipework is more to avoid the flexible corrugated pipes you now often see on gas meters these days.


       - Andy.


    Then if the regs. are referring to a flexible pipe they should use the word "flexible." or "non rigid". No, the regulation says "hard", The opposite is not flexible but soft..


    If it was a gas pipe there is NO WAY that I would apply a bonding clamp on it. Lead melts at the low relatively temperature of about 330 degrees C. A nice big diverted neutral current could cause a house explosion. No, hard metal means iron or steel or copper.


    LOOK.  Cooking with lead........

    Melting Lead On A Stove - Bing video


    Z.


  • 0
    wallywombat:

    Note that the damp cellar walls and floor are likely to be at a similar potential to the lead pipe (and to the general mass of earth surrounding the cellar).


    Yep, most damp earth and damp floors are at earth potential.


    Z.


  • Former Community Member
    0 Former Community Member
    wallywombat:

    Note that the damp cellar walls and floor are likely to be at a similar potential to the lead pipe (and to the general mass of earth surrounding the cellar).


    https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=56540&messid=466255&parentid=465200&FTVAR_FORUMVIEWTMP=Branch


  • 0
    I would not want to fix a clamp onto soft lead.

    There's nothing soft about lead water pipes on incoming mains water supplies. As they have to withstand 10 bar or more they're very thick walled - the ones I've cut out looked 25mm or more outside diameter but the inside was smaller than a pencil. You'd have difficulty crushing them with a lump hammer never mind as BS 951 clamp.


    Lead gas pipes (and perhaps water pipes fed from a cistern) are a different matter - has they had to withstand far lower pressure they were usually much thinner walled - so more care is needed. The old trick was to put the clamp over a joint to copper or meter tail - where the lead pipe would be reinforced by a copper or brass tube inside it. I reckon the reference in the regulations to hard pipework is more to avoid the flexible corrugated pipes you now often see on gas meters these days.


       - Andy.
  • 0
    Forget about it being water. It is extraneous to the house . It may also be connected to the MET of another house. Something earthy coming into your house from another house is a pretty good reason for a protective bonding conductor.
  • 0
    geoffsd:


    Also - the stop-cock is irrelevant and is mentioned nowhere in the regulations.


    Correct it doesn't say 'Stop-Cock' but 544.1.2 does say the connection shall be made to the consumer's pipework.  Where this starts is at the output of the meter for Gas.  For water it's a bit more arguable as if there is an external stop tap then all the pipework from there is the Consumer's responsibility, according to the water company so the internal stop cock may then be inserted in the consumer's pipework, and may not be the demarcation point.


  • 0
    Note that the damp cellar walls and floor are likely to be at a similar potential to the lead pipe (and to the general mass of earth surrounding the cellar).
  • 0
    Alcomax:

    But it is a damp cellar, probably victorian brick floor or flagstones. What happens if you are barefoot, checking the stop tap and that lead pipe imports a fault from next door? Ok, a reason for being barefoot; you were just having a shower and the water went off, so you amble down to find out what is going on. Or forget barefoot; the CU is metal and readily accessible with the lead pipe.


    Just cover the water pipe with electrically insulating material, or box it in, then it can't be touched. Out of sight and out of mind, and all that jazz.


    Z.


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