Introduction

Older homes often have receptacles and fixtures that are ungrounded, and many local codes do not require that they be rewired so they're grounded. Still, grounding is worth adding to your system because it adds protection against electrical shock. Grounding provides a third path for electricity to travel along, so if there is a leak of any sort, it will flow into the earth rather than into the body of a person who touches a defective fixture, appliance, or tool.

An electrical system is grounded with a grounding rod driven at least 8 feet into the ground outside the house or connected to a cold water pipe. Each individual branch circuit must be grounded as well, either with a separate wire that leads to the neutral bar of the service panel or with metal sheathing that runs without a break from each outlet to the panel. (In theory, electrical outlets can be grounded individually, but this is impractical.)

In some locations of your house -- especially where the outlet and/or appliances may become wet -- ground-fault circuit-interrupter (GFCI) receptacles are required (see Installing GFCI Receptacles, Related Projects). Older, ungrounded circuits usually are protected by polarization, which is less effective than grounding but better than nothing. Grounded and polarized receptacles work only if they are wired correctly. See Testing and Replacing Receptacles, Related Projects to test for this.