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My house is being re-piped by replacing all of the copper with PEX starting at the water service entrance. I'm on a well which is 150' from the house and the service line is CPVC. Currently, there is a ground connected to the copper cold water side of the water heater which connects to the neutral side of the main electrical service panel. There is also a ground to a grounding rod at the service panel.

My question is what to do with the ground connected to the copper at the water heater? I'm assuming it is only there to bond the copper in the house for safety and since all of the copper is being replaced with PEX it is no longer required. The copper wasn't being used as a second ground because the water service to the house has always been plastic to the foundation.

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There are a few things:

  1. In your main electrical panel there should be a ground wire connecting to the ground rod. If there is another ground wire connecting to the homes plumbing (or from the ground rod to the plumbing), the main electrical service is using your homes metal plumbing as a second ground. Even if the service line is plastic, the metal pipes may be an effective ground if some of them are in contact with earth or a concrete foundation. Thus if you are removing some of the original ground system of the home, you may need to add an additional ground rod. It's a good idea nonetheless. New code specifies 1 ground rod measuring less than 25 ohms or 2 ground rods >6ft apart regardless of the measurement. Since the measurement itself is difficult most electricians just put in two.

  2. There should be a ground conductor running from the main panel to the water heater and connected to the water heater at the terminal block of the water heater. If there's not, add one. If the branch circuit for the water heater is run in metal conduit, the conduit itself is the ground and should be connected to the water heater according to the manual of the water heater.

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  • Thanks for the quick reply. What you said is pretty much what I expected but I'm still not sure how the copper could have been used as a second ground. The foundation is a slab and all of the copper piping going through the slab is encased in black plastic pvc to protect it from the concrete and with the service connection being plastic it seems to me the copper was totally isolated from ground?
    – jimbo
    May 29, 2019 at 15:42
  • Are you replacing the copper encased in plastic that runs through the slab with PEX? That sounds.....difficult.
    – Martin Vandepas
    May 29, 2019 at 15:58
  • Why are you replacing all this copper water supply piping? Did it have leaks? Is the new piping to be brought in above the slab or under it?
    – Jim Stewart
    May 29, 2019 at 18:58
  • No, all of the copper in the slab is abandoned and new lines are run through the attic and walls. I have already had one slab leak and another pin hole leak in a wall. Once you have one pin hole leak odds are more will follow. A whole house repipe is not as unusual as it sounds, at least not around here. Copper was great in the past but my understanding a lot of copper production went overseas in the late 90s and things went down hill from there.
    – jimbo
    May 30, 2019 at 22:24

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