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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?
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    lead and making ingots at home. So easy. Could you do that with copper?


    Yes, but not so easily - lead you can melt in a steel baked bean can on the BBQ, copper would require forced air probably to heat a reasonable volume to melting temps with charcoal. Brass is slightly easier - a brazing torch will do it (the clue is in the name, but Brass melts at ~ 900C or so, copper more like 1080C. Lead at 330C if pure, less in soft solder).

    To melt a lead pipe electrically however would require a fantastic number of amps, unless you could draw an air arc to get some local heating, and with plasma then the choice metal is neither here nor there, you can melt pretty much anything. However as various folk trying to trip AFDDs have found getting an arc to sustain to a low melting point metal is quite hard, it tends to migrate and either fuse to dead short so the arc goes out, or burn back until the gap increases to the point where the arc goes out.

    Mike.
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    Compression fitting can be used on copper pipe and no solder is required.

    In theory perhaps, in practice copper gas pipes are soldered (other than for the final joint for an appliance). So really lead pipework in no worse than copper - the solder is still the weak link in both systems you're likely to find in the real world.


    Besides if it was at all credible that you had enough current flowing through the bonding to get the pipework to hundreds of degrees - what state would the 10mm² bonding conductor be in? (even thin walled 15mm copper pipe has a copper c.s.a of around 30mm² - lead pipes have a lot more metal that likely makes up for its higher resistance)


       - Andy.
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    Andy, melting lead and making ingots at home. So easy. Could you do that with copper?



    Z.
    https://www.bing.com/videos/search?q=melting+lead+pipe&docid=608005659388946246&mid=609C4A9976D60FF3A237609C4A9976D60FF3A237&view=detail&FORM=VIRE
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    Zoomup:

    What I said was that I would not fit a B.S. 951 earthing clamp onto a lead gas pipe. Nothing more nor less.


    What does the Standard have to say about the types of pipe that may be used? (I have not got a copy and have lost my library access for the time being.)


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    AJJewsbury:
    One of my concerns about using lead is its low melting point, perhaps when carrying large fault currents. Domestic lead covered cables of old were perhaps fused at 5, 15 or even 30 Amps so fault currents were relatively small. With lead pipes that may carry large diverted neutral currents the lead may melt or or best become soft, so fitting a B.S. 951 earth clamp to a lead gas pipe could be dangerous. I would never do so. Lead melts at about 300 degrees C and copper at over 1,000 degrees C.



    Are you really suggesting that if you worked on an installation where all the gas pipework was all lead, you'd leave it unbonded?


      -  Andy.


    I don't think that an all lead gas pipe system in a house would comply with modern gas regs. these days Andy.


    What I said was that I would not fit a B.S. 951 earthing clamp onto a lead gas pipe. Nothing more nor less.


    Z.


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    AJJewsbury:
    One of my concerns about using lead is its low melting point, perhaps when carrying large fault currents. Domestic lead covered cables of old were perhaps fused at 5, 15 or even 30 Amps so fault currents were relatively small. With lead pipes that may carry large diverted neutral currents the lead may melt or or best become soft, so fitting a B.S. 951 earth clamp to a lead gas pipe could be dangerous. I would never do so. Lead melts at about 300 degrees C and copper at over 1,000 degrees C.

    I'm sure you're worrying over nothing. Copper pipework is no more resistant to heat than lead pipework - as both will fail well below 300 degrees when the solder in the joints melts. If it's not an issue with copper pipes why should it be with lead ones?

     


    Blowlamp flame on copper pipe: pipe remains intact.


    Blowlamp flame on lead pipe and it will melt.


    Compression fitting can be used on copper pipe and no solder is required.


    Z.


     


  • 0
    One of my concerns about using lead is its low melting point, perhaps when carrying large fault currents. Domestic lead covered cables of old were perhaps fused at 5, 15 or even 30 Amps so fault currents were relatively small. With lead pipes that may carry large diverted neutral currents the lead may melt or or best become soft, so fitting a B.S. 951 earth clamp to a lead gas pipe could be dangerous. I would never do so. Lead melts at about 300 degrees C and copper at over 1,000 degrees C.

    I'm sure you're worrying over nothing. Copper pipework is no more resistant to heat than lead pipework - as both will fail well below 300 degrees when the solder in the joints melts. If it's not an issue with copper pipes why should it be with lead ones?


    Diverted N currents can flow in service cables just as readily as gas pipes - if the lead sheath of PILC cables doesn't melt (or the sweated/soldered connection to it), why should the lead gas pipe?


    Are you really suggesting that if you worked on an installation where all the gas pipework was all lead, you'd leave it unbonded?


      -  Andy.
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    mapj1:

    Why do we worry about current in a lead sheath more or less than in a steel armour on a modern cable ? - if anything the lead has a larger cross-section, is better cooled due the larger surface area...

     


    This American video confirms the robustness of P.I.L.C. cables.

    https://www.bing.com/videos/search?q=youtube+terminating+PILC+lead+cable&docid=608021297359238224&mid=2B0334B9E1D44F83AB9D2B0334B9E1D44F83AB9D&view=detail&FORM=VIRE


    Z.


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    Also, the N.I.C.E.I.C. says that adding a B.S. 951 earth clamp should not be done to a P.I.L.C. service cable in an installation. It is wrong because the cable is not the house owner's property. Also the potential problem of the clamp loosening is a concern. (See previous link above).


    Even the 1966 A.S.E.E. Guide to the I.E.E. wiring Regulations.... said that the earthing connection at a metal service cable assumes consent or provision by the supply authority, and where not available another form of earthing must be adopted.


    Z.
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    mapj1:

    Why do we worry about current in a lead sheath more or less than in a steel armour on a modern cable ? - if anything the lead has a larger cross-section, is better cooled due the larger surface area and and if anything paper and oil not exposed to air is likely to be more robust than XPLE  insulation in terms of failure modes if it heats up.

    I agree once the lead is damaged or not connected, then you have a problem, but that is true of any armoured cable.

    Mike.

     


    One of my concerns about using lead is its low melting point, perhaps when carrying large fault currents. Domestic lead covered cables of old were perhaps fused at 5, 15 or even 30 Amps so fault currents were relatively small. With lead pipes that may carry large diverted neutral currents the lead may melt or or best become soft, so fitting a B.S. 951 earth clamp to a lead gas pipe could be dangerous. I would never do so. Lead melts at about 300 degrees C and copper at over 1,000 degrees C.


    Back in the 40s a device called a "Pyrotip" was used to "Burn" lead for jointing. The manufacturer was the General Electric Company of  Schenectady. The heating source was electrical in the form of a step down transformer to a carbon electrode. The work was connected by a clamp to one terminal and the carbon rod to the other. The p.d. was insufficient to form an arc. The lead was melted only by the power dissipated in the carbon rod and that dissipated in the contact resistance between rod and work.

    So in this case electricity traveling through the rod and lead, was a friend to melting lead, in other cases I am concerned about gas leaking from damaged lead pipes.


    Z.


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