No announcement yet.

Current Measured on water and gas lines

  • Filter
  • Time
  • Show
Clear All
new posts

    Originally posted by LarryFine View Post
    There may well be a neutral issue feeding more than one house, making it between the utility transformer and the distribution points.
    M.E.N. in close proximity w/metallic municipal systems all common to the serving xformer....?



      If you have continuous metal piping connecting to all houses in the neighborhood and all of them are bonded to the electrical service grounded conductor - you have a huge network of parallel paths. Even if there are multiple transformers in the neighborhood, they are all bonded together via a MGN. There is somewhat unlimited number of paths for current to flow.

      When you have parallel paths current takes all those paths. The lowest resistance path carries the majority of the current but all paths do carry some current. This is why even when OP has the main breaker open, there is still some current on the water line, it is current from that network and the portion of it that happens to be flowing in that path. As long as that network remains intact there is nothing you can do to prevent those currents from straying throughout the network. The biggest danger here is for the plumber that opens the path when working on the piping.

      Since 1996 NEC we have been required to run GEC to the first five feet of piping after it enters the structure. This does help limit that current path to only the first five feet of piping into the structure, and the risk to the plumber typically only involves first five feet of pipe or if they would be opening something outside the house in the main supply.

      If this is an older application that has the GEC landed somewhere besides within first five feet of entry - you can move the GEC to within first five feet and that will at least remove current from other piping through the house, presuming there is no second pipe leaving the house that makes up an additional path in the neighborhood network, metallic water line to an outbuilding that also has electricity on same property would be an example that might still leave you with troubles.
      I live for today, I'm just a day behind.