Bonding building metal piping systems

Bonding Pipes in Your Home or Business Property

Exposed metal piping systems in a building should have zero voltage between them, and a low-impedance path to ground. In many homes, all of this may be ensured by bonding hot and cold water pipes, and gas pipe, to each other where they converge at the water heater (if gas-fired). Contrary to popular belief, water is a poor conductor, and some fittings at or inside water heaters could insulate the hot and cold piping systems from each other. So intentional, solid metal bonding between all pipes ensures voltage (potential for current flow) cannot build between different piping systems, and that any voltage induced on the bonded system (for example, from a nearby lighting strike or from a damaged conductor in the building wiring system) will conduct to earth via a robust fault current path. Lightning-induced voltage will cause less damage when it has a robust path to earth, while circuit faults shorting to well-earthed piping will draw current through the circuit breaker to trip it, rather than remain a latent fault that could ignite a fire or shock or electrocute people.

System Grounding First

A robust path to ground from the piping systems is ensured only if the electrical service equipment has been properly grounded and bonded in accordance with National Electric Code (NEC). There should be a grounding electrode conductor (GEC) from the service disconnect equipment to a metal water service entrance pipe (if metal and installed through earth), and to a supplementary driven ground rod or other electrode. Additionally, the connection to the water pipe should include a bonding jumper that maintains the connection, even if the water meter is removed for servicing. The electric service bonding connects the electric utility grounded conductor and the local grounding system to local earth, equalizing any voltage that might otherwise exist between the utility ground (potentially 100′s of yards away) and the earth under or around the building. Such concerns do not arise often (or obviously) during normal use, but localized voltages resulting from lightning strikes, induced at-a-distance (without need for direct strikes) will cause less damage if local bonding in your building is thorough.

95% of existing construction homes in this neighborhood lack this important part of the building grounding system, which ensures that most or all metal in the house has a way to drain transient surges induced by nearby high-voltage lightning strikes. The high-voltage current flow of a lightning discharge to earth, perpendicular to some metal in the house, induces current in the metal, at-a-distance, even if the strike does not directly contact your building. Bonding of the metal piping systems minimizes induced voltages and the risk of fire.

Low Materials and Labor Cost

The materials costs for bonding metal piping systems are less than $30, while labor will typically be a service call of $65-100 (or DIY: ‘free’), or $25 if part of a work order $250 or more.

Up to parent:

• What is grounding-and-bonding?

See also:

• Flexible gas tubing (CSST) may be ruptured by lightning-induced discharge
  • Suggestion: where CSST is used between sections of cast-iron pipe, perhaps a bonding jumper should be installed across the iron pipes to ensure most lightning discharge energy runs around the CSST rather than through it.