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Thread: bonding sewer line.

  1. #1
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    bonding sewer line.

    after a house I went to this week, occurred to me that you bond metal water lines, gas lines, etc. ever heard of bonding copper /galvanized/cast iron sewer lines? most stuff now is pvc, so no issue there.

    older home it seemed everything was carrying current due to electrical issue, which brought up the thought
    Col 3:23


    questions asked, answers received, ignorance abated

  2. #2
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    May 2019
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    So here is a situation for an old farm house in the country:
    Guy sitting in tub full of water would feel tickle of electricity when he touched the faucet.......enough to make one give up bathing.
    Faucet was wall mounted above tub IIRC.

    Private well, grounding to pump OK, windings not shorted to ground.
    Electric water heater elements checked, not grounded into water at all.
    Electric dryer checked and unplugged.
    Electric panel neutral/ground connection was solid.
    Ground rod at panel, ground rod at pole mounted meter socket.
    Hot and cold copper lines were bonded to electric panel.
    No gas line, no ductwork.
    Connections looked good at the top of power pole.
    All connections in meter socket/transfer switch were solid.

    The tub drain was galv pipe running out of the house and buried for maybe 30' and connected to the outlet of the septic tank.
    Other than the tub all other drainage was PVC.

    There were milivolts between the cast iron tub drain and the copper water lines.

    From previous problems with stray voltage in dairy barns the remaining solution seemed to be a bad power company neutral connection possibly miles away.
    This farmstead was at the end of perhaps a 1 mile line.
    The 7200 volt primary used a hot and a neutral that is grounded.
    If a splice in the neutral anywhere upstream is faulty (high resistance) then some of the return current will flow down to the ground rods which are at each pole.
    Then that stray current will seek another return path.
    It will travel thru the earth in all directions and consequently thru the iron drain pipe and CI bath tub.
    The person in the tub completed the circuit to the grounded piping when he was sitting in the water touching the faucet.

    I called the power company with my conclusion, they understood completely and got right after the problem.
    I think getting shocked sitting in a tub of water put this at the top of the list for the day.
    There have been lawsuits concerning stray voltage as it affects milk production, so this might have taken priority over even that.
    I don't know where they found the problem but it was corrected and the stray voltage went away.

    You can find defective connections with a digital volt meter. Measure across the connection and if any voltage showing you replace that splice. Just like finding bad contacts in a compressor contactor.
    Same in a meter socket, check between the actual conductor ahead of the lug and the actual conductor below the other lug of a neutral bar.
    Often aluminum wire connections in lugs can become high resistance but still look good.

    A ground clamp was added to the galv pipe to bond it to the water system. This put all metal at the same potential by bonding everything together. As one would do in dairy barns.

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  4. #3
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    Thread Starter
    every meter socket i see, check the hub for weathertightness. water gets in the hub or se cable will corrode the neutral. the job this week also had evidence of water getting in meter and running down se cable onto main breaker in panel box.
    Col 3:23


    questions asked, answers received, ignorance abated

  5. #4
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    Quote Originally Posted by billygoat22 View Post
    after a house I went to this week, occurred to me that you bond metal water lines, gas lines, etc. ever heard of bonding copper /galvanized/cast iron sewer lines? most stuff now is pvc, so no issue there.t
    I've seen drain lines bonded when there was some voltage between drains and supply pipes, but that was kind of a band-aid on some bigger problem. Generally cast iron isn't bonded though. Conductivity between sections is pretty bad, especially on newer cast iron with the sort of rubberized coating. It's largely up to the AHJ's interpretation of NEC 250.104(B), so the question is are the pipes "likely to become energized?"

  6. #5
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    Thread Starter
    had a house where a lot of power must have been looking for a ground, and didn't see much of a ground in the house, or bonding, which got me thinking. even the duct in basement had arcing spots between the boiler piping and a duct hanging strap.
    Col 3:23


    questions asked, answers received, ignorance abated

  7. #6
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    Sewer lines have a very poor electrical connection. My vote is for whoever called out the power company to correct problem. Recent storm here, waiting for them to pull tree limb off live wires.
    " The more I learn the more I realize how much I don't know"

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