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Thread: Bonding two sections of copper pipe with PEX between them?

  1. #1
    DIY Senior Member BimmerRacer's Avatar
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    Default Bonding two sections of copper pipe with PEX between them?

    Most of the house is copper. I replumbed a portion for master bath, two hose bibs and basement bath using Uponor manifold system. I transition back to copper for the basement bath, and hose bibs.

    Do these copper segments need to be bonded back to the main supply before it first transitions to PEX? I saw something about 5' rule but didn't quite understand it.

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    Electrical Contractor/Instructor jwelectric's Avatar
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    The first five feet is if it is an electrode or if there is at least ten feet in contact with earth.

    With the introduction of the nonmetallic piping in your system there is not need to bond any part of the metal water pipe unless there is an electrode as outlined above.

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    DIY Senior Member BimmerRacer's Avatar
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    Thank you. I recently reconnected supply to the basement bath and discovered that I get "energized" water when I turn on the vanity light switch. I verified that it's not in my hand by touching hot wire and copper pipe with electrical tester. I plan to remove drywall and look at the romex supplying that vanity light. Since nothing else has changed in terms of elecrical or plumbing in that room, could this problem have been masked by the fact that old pipes were all copper and therefore grounded? The vanity light wall box is metal and is supplied with 14/2 wire with ground. The position of the box is likely that it's touching the copper pipe, but I do not know for sure right now, until I open up the wall

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    Electrical Contractor/Instructor jwelectric's Avatar
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    Touching you meter to the hot wire and the metal water pipe and reading a voltage in no way means that your water is energized.

    What it does mean is that the hot wire is energized.

    Pure H2O does not conduct current but we all know that even distilled water has impurities and some of these impurities will conduct current. I would be expecting to get a voltage reading when reading to a water pipe if somewhere on that water pipe there is a connection back to the service. Should there be a water heater that is wired to the service the equipment grounding conductor of that circuit is more than enough to complete the path and give a voltage reading in the application you have described.

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    DIY Senior Member BimmerRacer's Avatar
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    So, I ripped out the drywall and the metal box from the vanity light was definitely touching the copper pipe. Romex wire looks fine now that the box is not touching I don't get zapped nor get any reading on the tester when I touch hot wire and the pipe.

    before and after




  6. #6

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    Good detective work!

    Now what was the cause?

    There should be a wire clamp on the wire going to that box which prevents the sharp metal of the box from cutting into the wire.

    Or perhaps there was a loose wire on the light fixture touching the metal of the fixture, then that was connected to the electrical box via the screws, and then to the pipe?

  7. #7
    DIY Senior Member BimmerRacer's Avatar
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    There's a strain relief clamp and I had tossed the actual light fixture a few days before. *shrug*

  8. #8

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    Well that's even better...

    Get a new fixture and be sure the electrical box/wires look ok, and you should be all set.

    Problem solved!

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    DIY Senior Member Jeff1's Avatar
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    Is the metal box grounded properly? I can't tell from the picture.

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    DIY Senior Member BimmerRacer's Avatar
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    As far as I recall, the ground wire was wrapped around a grounding screw inside a the box.

  11. #11

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    Good point!

    If the pipes and the electrical box were properly grounded, this would not have happened!

    Check that the metal electrical box is properly grounded, that the new light fixture is properly grounded if metal, that the ground in the wire is good, and the main electrical system grounds are ok.


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    DIY Senior Member BimmerRacer's Avatar
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    easiest way to test for proper ground? Can I use the two probe Ideal tester? I did use it last night by touching the hot wire and the box and the result was the same as when I touched the copper pipe before, when the metal box was touching it - it showed 110V

  13. #13

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    I use an ohm meter myself. This is a setting on a multimeter. Sort of like a "continuity" test, but better and more feedback/accuracy of testing method.

    If you have a long extension cord, measure the "ohms" in one wire from the plug to the outlet. Disconnected of course. You will get a certain reading in ohms and this will be low. The longer the wire, the more ohms. Then try a short extension cord and see the difference.

    So based on the length of wire, you would expect to see a certain ohms reading from one point to the other end.

    Sometimes people don't do things right and they don't bother to connect ground wires at all! So in this case, there would be no ohms reading.

    Or there may be a poor connection along the way. In that case a high ohms reading.

    The best ground system is two ground rods placed 6 ft. apart at the main electric panel.

    So what you can do to test this, is place the end of a long wire (cheap speaker wire or whatever just for testing) on one of the ground rods. Then run the wire into your bathroom, then use an ohm meter to measure the ohms from the end of that wire to the ground on the outlet. The ohms reading you get should be consistent with that length of wire (also taking into account the cheap speaker wire).

    If there is electricity present and this is shorting to ground at one end, this could wreck your ohm meter! So best to turn off the main power for this test.

    Basically you are testing that the ground wire is contiguous from that outlet box all the way to the ground rods (or cold water pipe ground if you have that).

    How to use an ohm meter...
    http://www.ehow.com/how_2282412_use-ohmmeter.html

  14. #14

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    P.S. You would also want to check the pipes with the long wire and ohm meter to be sure they were also properly bonded back to the main ground.

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    DIY Senior Member BimmerRacer's Avatar
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    Jeez Bob, last time I had to use Ohm's law was back...oh, longer than I can remember. Not sure that's the route I will go with this, but thanks for the refresher.

    I know the pipes in the bath are not bonded, and according to what jwelectric said they do not have to be. I know you said otherwise over at DIYChatroom.

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