Code requires the metal water piping system in a home to be bonded to the electrical system. Bonding connects the metal piping to the grounding system so it stays at the same electrical potential and does not become a shock hazard if it were to contact an energized conductor. This is a standard electrical safety requirement, separate from, though related to, the question of whether a water pipe serves as a grounding electrode. Understanding it clarifies this piece of your home’s electrical safety.

Here is what the code is for bonding metal water pipes.

What bonding the water piping means

Bonding the metal water piping means connecting it to the electrical system’s grounding, typically with a bonding conductor from the piping to the grounding system at or near the service. This ties the piping into the same grounded system as the rest of the home’s metal parts, so they are all at the same electrical potential.

Code requires this bonding for the metal water piping system in a home, and the bonding conductor is sized according to the applicable requirements.

Why code requires it

The reason for bonding metal water piping is safety. Metal pipes run throughout a home and are often touched, including with wet hands. If a pipe were to become energized, for example from a fault where a wire contacts the plumbing, an unbonded pipe could present a serious shock hazard. Bonding ensures the piping is connected to the grounding system, so a fault clears safely rather than leaving the pipe energized. This protects anyone who touches the plumbing.

Bonding versus grounding electrode

It is worth distinguishing two related things about metal water pipes:

• Bonding the piping, which this article covers, means connecting the metal piping to the electrical system for safety, so it cannot become a shock hazard.
• A water pipe as a grounding electrode, which is when a qualifying metal underground water pipe is used as part of the grounding electrode system that connects the system to earth.

These are related but distinct. A home may both use a qualifying underground metal water pipe as an electrode and bond its metal piping, and code addresses both.

What about homes with plastic pipe?

Many homes have plastic water piping, or a mix of plastic and metal. Plastic pipe does not conduct electricity, so the bonding requirement applies to the metal piping that is present. Where piping is plastic, there may be little or no metal piping to bond. An electrician identifies what piping a home has and bonds the metal portions as required.

Why a professional handles it

Bonding metal water piping correctly, with a properly sized bonding conductor connected at the right location, is a code-governed task. It is part of the overall grounding and bonding of a home’s electrical system, which must be done correctly for safety. A licensed electrician handles water pipe bonding as part of service work or when correcting grounding and bonding, and it is verified during inspection.

Code requires a home’s metal water piping to be bonded to the electrical system, connecting it to the grounding so it stays at the same potential and cannot become a shock hazard if it contacts an energized conductor. This bonding is separate from a water pipe serving as a grounding electrode, though code addresses both. Homes with plastic pipe have little metal to bond. Because it is code-governed and safety-critical, a licensed electrician handles water pipe bonding.

Stella Electric handles grounding and bonding, including metal water piping, for homeowners across the Baltimore area and throughout Maryland, with flat-rate pricing and no overtime charges. If your bonding needs attention, we can help. Financing is available on qualifying projects.