code question, grounds, metal pipe

Discussion in 'General Plumbing Help' started by pasadena_commut, Apr 26, 2019.

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  1. Apr 26, 2019 #1

    pasadena_commut

    pasadena_commut

    pasadena_commut

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    Hi all,

    My house currently has galvanized pipes everywhere. The electrical service has a ground which runs down the wall from the breaker box and clamps onto a pipe which in one direction goes to the back sprinklers and in the other to the rest of the plumbing. (Probably less than 10 ft total in the dirt in the backyard , but not much less, maybe 8?.) We are going to replace the main water line and the code apparently (have not seen it myself yet) says that the final 10 ft. of that must be metal. That makes perfect sense as long as the rest of the galvanized pipe remains - it grounds the electrical service through the wire, to the clamp, then through the house pipes to the earth. However, if we repipe with PEX there would no longer be an electrical connection between the breaker box and that 10ft of pipe on the main line, so that 10ft of metal would no longer do anything useful.

    What happens in that case?

    Other grounding methods exist, like driving a rod deep into the dirt and attaching the electrical service ground to that. Does code allow that mode of grounding or is there some specific reason they want a long ground wire run all the way under the house to that specific 10ft of water filled metal pipe in the front yard?

    The main point being, I don't see any particular advantage to grounding the electrical service to an isolated chunk of metal pipe filled with water when alternative grounds are available. If we were to bury a 20 ft long thick copper rod near the plastic water pipe, and run a ground wire to that, that seems like it would be an adequate ground, as would a 10 ft rod driven into the ground near the breaker box.

    I am not averse to copper pipe per se, but one of the contractors I spoke with said to try to avoid it in our area because the chloramine levels in the water supply are high and people have had a lot of problem with pinhole leaks. He wasn't against copper generally and said he used it a lot in regions without the chloramine issue.
     
  2. Apr 26, 2019 #2

    gagecalman

    gagecalman

    gagecalman

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    There are specific code requirements that deal with grounding and bonding when you have metal pipes.
    You might want to post your question at https://www.houserepairtalk.com/. Lots of great info on the subject.
     
    Last edited by a moderator: Apr 26, 2019
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  3. Apr 27, 2019 #3

    FishScreener

    FishScreener

    FishScreener

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    Grounding to metal plumbing is now seriously discouraged. Just because of incidents expressed in your question. Replacement of a piece of pipe with pex or pvc can lead to an unbounded “ground”, and the ground can become a guy in the shower reaching over to turn off the water while standing in the wet shower.

    The correct solution is to add real ground rods, and/or if possible bond to the reinforcement in the in the concrete.
     
  4. Apr 27, 2019 #4

    frodo

    frodo

    frodo

    Just call me Macgyver Professional Supporting Member

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    We usually re-pipe the house and abandon in place the old pipe
    thereby not breaking the electrical bond with the earth.
    if we are requested to remove the old pipe, we buy a grounding rod and install it
     
  5. Apr 28, 2019 #5

    pasadena_commut

    pasadena_commut

    pasadena_commut

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    The former seems like the best policy in old houses like mine. I know of three points where parts of the electrical system are grounded to the water pipe, not including the ground at the breaker box. Installing a grounding rod at the breaker box would satisfy that problem but leave the other 3 floating. Two of those grounds use really skinny little wires run down from sockets to water pipes below. The third is for the garbage disposal, which is grounded by a clamp onto the cold water pipe under the sink. The electrical system in this house does not have ground wires anywhere, but a few outlets are fed by shielded cables from the service box and are are grounded through that metal shield.
     

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