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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
    I see little actual point in bonding such a short section of water pipe, but would be inclined to do it anyway to avoid any future pedantic inspector failing the installation due to "no main bonding"


    Bonding after the stop cock is a requirement for two reasons, firstly a threaded joint with PTFE tape connecting the pipe to the stopcock can introduce significant resistance, and secondly a replacement might be plastic.
  • 0
    I think that the change to non-conducting pipe is sufficiently close to the point of entry to fall within the scope of the exemption in 411.3.1.2, but I share broadgage's concern about future inspections.
  • 0
    I have seen the rumoured  bonded short length of 15mm copper pipe inserted into a plastic pipe, in a house with all plastic pipework, after the stopcock with a plastic supply pipe. I took a photo but it has disappeared during one of the many phone/computer upgrades/changes.
  • 0
    I fail to see why introducing a hazard by bonding isolated pieces of pipe should be done just in case an inspector might not know what he is doing.


    Also - the stop-cock is irrelevant and is mentioned nowhere in the regulations.
  • 0
    I was pulled up on this once by a meter man, he insisted I changed the bond position on a stop tap coming out of the floor. The only problem was that this was not the main stop tap, it fed the Greenhouse! The main incoming pipe was 2" but wasn't by the meter position and was bonded too. One cannot tell some people.


    In the case of the OP, there is little danger, as most of us don't play with the CU and a water pipe at the same time, but I suppose a couple of feet could be done, so a bond is easier.  As for BS 951 clips on plastic pipes, I found one at a swimming pool once (75mm pipe), blue and all. There was even the safety notice attached. I quizzed the company on why, and they said the incoming water needed to be "discharged". Wonderful.
  • 0
    When I lived in London, the local authority had a program of inspecting and licensing HMOs.

    The inspector came with a simple tick list and one tick was "safety earthing of mains water" no mention of pipe material or other circumstances.

    If seeking a licence it would be much cheaper and simpler to apply a needless earth bond, than to argue the point and pay for a second visit.

  • 0
    Why must any bonding be done after the main stopcock?

    I think that was only really intended for gas - as the gas people have a habit of deliberately introducing an insulating joint (IJ) specifically to stop diverted N currents flowing through their pipework - and where present these are usually incorporated into the valve/meter assembly. So bonding on the supply side would completely defeat the insulating joint, while bonding on the consumer's side is almost identical if there isn't an IJ, and likely harmless (if pointless) if there is.


       - Andy.
  • 0
    Aren't we supposed to apply the bonding clamp to hard metal. I would not want to fix a clamp onto soft lead.


    544.1.2


    Z.
  • 0
    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.
  • 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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