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Locale: WA State, U.S.

Inspector approved gas plumbing and followed up later, saying: "Please note that we will be verifying the bonding of the new gas piping at the next inspection, please contact L&I for any questions regarding electrical. "

Gas plumbing will be connected to tankless water heater via flex hose. I'm assuming the flex hose doesn't count as proper bonding for the gas plumbing. So can I run a ground wire from the electrical outlet where the gas water heater will be plugged in or even bond to the water heater directly (since it is grounded via outlet plug)?

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  • What type of "flex" is used for the gas connection in question? Are you talking about CSST, or an appliance connector?
    – ThreePhaseEel
    Sep 24, 2020 at 23:09

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Grounding and bonding is a whole chapter in NEC. They're not all just the same thing.

Not least, every house has 2 different networks:

  • The Equipment Safety Ground which carries grounds from the service panel to all the appliances and outlets. This travels alongside the live conductors, as the green, yellow-green or bare wire in cables or conduits (or in the case of EMT, IMC or RMC, the conduit shell itself).
  • The Grounding Electrode System, which is the bond between the service panel and the actual earth: It is the heavy bare copper wire going from the service panel to ground rods, Ufer ground, or water main. (water main grounds are getting dicey because of smart meters).

The gas main should be bonded to the house's Grounding Electrode System.

It definitely should not be connected to any part of the Equipment Safety Ground network that serves subpanels and appliances.

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  • Perfect. This separation of the two systems by the service panel is exactly what I was wondering about. Thanks for directly addressing that!
    – Jake Hassings
    Sep 25, 2020 at 19:44
  • One additional thing: what does the inspection for this entail? I'll check NEC, but I've read they just need to test and make sure resistance is low enough. I want to make sure I'm prepped and ready to go for the inspector with what he needs to see.
    – Jake Hassings
    Sep 25, 2020 at 19:46
  • @JakeHassings generally 1 ground rod needs to be tested, but two rods are presumed good enough. Many people just set 2, since it is cheaper than the test.
    – Harper - Reinstate Monica
    Sep 25, 2020 at 21:39
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The water heater's equipment grounding conductor takes care of its side.

Check the installation manual (example) for your CSST (Corrugated Stainless Steel Tubing; the bright yellow, flexible gas pipe.) You should be bonding the gas piping at your service entrance to the home's grounding system. That's what the inspector is referencing.

Some additional information: http://csstsafety.com/CSST-solution.html

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    For those not in the know, what is "CSST"? I don't see any explanation in your answer or in the OP's question.
    – FreeMan
    Sep 24, 2020 at 15:17
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    Good suggestion, @FreeMan. I edited my answer to clarify CSST is the flex gas tubing.
    – Jeff Wheeler
    Sep 24, 2020 at 15:24
  • Excellent, thank you!
    – FreeMan
    Sep 24, 2020 at 15:30
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    Corrugated stainless steel tubing is the full name for most flex gas tubing but not all. On the gas water heaters I have installed a grounding clamp was required on the csst at the water heater, silly since the frame is bonded but it has to be continuous to count.
    – Ed Beal
    Sep 24, 2020 at 15:36
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    Also, thanks for the manual link. On page 13 - section 2.7, it looks like bonding is needed for the CSST flex connector (connecting branch plumbing to appliance plumbing), in addition to the main gas plumbing (which is galvanized).
    – Jake Hassings
    Sep 25, 2020 at 19:53

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