Bonding a Metal Water Line with Mixed Materials
During a rough-in inspection of a single-family house, you find the 200 A service panel bonded to the metal water service pipe with a 6 mm² copper conductor clamped to the pipe about 1 m from where it enters the foundation. The interior plumbing has been partly replaced: copper near the entry, then a section of PEX, then copper again at the fixtures. The electrician also ran a separate bonding jumper from the panel to a gas line. The water pipe's continuity through the building is therefore interrupted. The electrician says the bond at the entry is all that is required and the gas bond is extra credit.
1. Evaluate the water-piping bonding as installed and identify the defect.
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The bond at the point of entry is correctly placed for the metal water service, but the installation has a continuity problem. Because a section of PEX interrupts the metallic path, the downstream copper piping is no longer reliably connected to the entry bond. Metal piping that is likely to become energized and is not continuously metallic must be bonded separately where it is isolated. The inspector should require a bonding jumper to the isolated copper sections, sized per the applicable table for the service rating, and should verify that clamps are listed for the pipe material and are accessible. The presence of PEX does not remove the requirement to bond the remaining metal piping; it changes where the bond must be made.
2. Assess the gas-line bonding jumper and state whether it should be approved, removed, or modified.
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Bonding metallic gas piping is generally required or permitted so that the piping does not become a path for fault current, but the bonding conductor must be sized and connected correctly, and the gas utility's rules also apply. The jumper should not simply be removed because the electrician called it optional. The inspector should verify the conductor size against the service rating, confirm the clamp is listed for gas pipe and is accessible, and confirm the connection point is acceptable to the gas authority. If the jumper is undersized or the clamp is not listed, it must be modified. If it is correctly sized and installed, it should be approved and documented, not treated as extra credit.