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Hobson's Choice?

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Q. You recently visited a bungalow to do some electrical work. The owners had just moved in. You had an opportunity to check the electrical installation. The main gas bonding was obvious as the 10.0mm2 green and yellow cable ran externally.


You looked under the sink in the base unit, but could really only see a copper pipe rising from the floor level up to the taps as the back of the cupboard restricted the view. A 3 inch (75mm) diameter hole had been cut into the back panel for the operation of the main water stopcock handle. There were other copper pipes visible as well. It was unclear as to the type of main cold water supply pipe. The bungalow was built in the 60s/70s.


You have an old  Minor Works Certificate  given to you for the bungalow. It states that the main water pipe may not be main bonded.


You are then given a very recent E.I.C.R. stating that the main water pipe is plastic and main bonding is not required.


Do you:


1. Main bond the water pipe?


2. Buy an endoscope and have a good look?


3. Do nothing? Trust the E.I.C.R.


4. Ignore the issue.


5. Rip out the kitchen base unit that obscures your view?


6. Ask Fred down the pub?


This site changes stopcock to stop c***


Z.

  • 0
    7/ mirror on a stick jobby ?
  • 0
    croc clip on handle of stop tap. Other croc clip to MET.  Measure resistance.

    Very low, say sub ohm,  do nothing - it may not be bonded in  quite the right place exactly  but it is already attached to the building earthing somewhere, and can't become that dangerous without firing a fuse or something.

    High res proceed to  verify if it is conductive to ground outside.

    Croc clip to garden fork outside. Meter on K ohms range. More than perhaps 20K ohms from stop tap to garden fork, consider it isolated, no bonding needed. 

    Anything lower then look for an easy place to bond to MET or to crimp a daisy-chain from the gas bond.


    edit due to recent further info. Add option to attack spiders with other meter on 1kV and Megohm range.
  • 0

    ebee:

    7/ mirror on a stick jobby ?




    That might work in some locations but the hole is very limiting, and the location is dark, and then there are the killer False Widow spiders that might lurk there. 


    Z.

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    or, 8. (presuming the gas is plastic out of the ground) Isolate the installation, disconnect supplier's earth, test between supplier's earth and water pipe/stop tap - if over 23k Ohms then water pipe can't be extraneous. (If not over 23k Ohms it's harder to tell - it still might not be as there might be parallel paths lowering the reading).


      - Andy.
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    AJJewsbury:

    or, 8. (presuming the gas is plastic out of the ground) Isolate the installation, disconnect supplier's earth, test between supplier's earth and water pipe/stop tap - if over 23k Ohms then water pipe can't be extraneous. (If not over 23k Ohms it's harder to tell - it still might not be as there might be parallel paths lowering the reading).


      - Andy.






    The combi gas boiler is in the loft and has many metal pipes running to it. All are very well bonded to each other. It is suspected that the metal water pipes are bonded via them. So the gas bonding would have to be disconnected to confirm extraneous conductive parts or not. Well if that is what it needs, that is what it needs.


    Z.

     

  • 0

    The combi gas boiler is in the loft and has many metal pipes running to it. All are very well bonded to each other. It is suspected that the metal water pipes are bonded via them. So the gas bonding would have to be disconnected to confirm extraneous conductive parts or not.



    I don't think so - with my procedure internal parallel paths don't matter - in effect we're testing whether the whole system is extraneous or not - if the gas is plastic coming out of the ground, and the water is too, then with the supplier's earth disconnected there should be little or no connection between the MET or any internal pipework to true earth. Any bonding between the MET and internal metal has pipework shouldn't affect that (nor the boiler c.p.c.).


      - Andy.
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    Headings should include subject matter, sufficient for searches or to advise the contents. It is most annoying to open posts and find no interest.


    Jaymack
  • Former Community Member
    0 Former Community Member
    Just bond the sink like most plumbers would do ...

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