Homeowners sometimes attempt to perform the following dangerous modifications to ungrounded receptacles:
- the use of an adapter, also known as a "cheater plug." Adapters permit the ungrounded operation of appliances that are designed for grounded operation. These are a cheaper alternative to replacing ungrounded receptacles, but are less safe than properly grounding the connected appliance;
- replacing a two-slot receptacle with a three-slot receptacle without re-wiring the electrical system so that a path to ground is provided to the receptacle. While this measure may serve as a seemingly proper receptacle for three-pronged appliances, this “upgrade” is potentially more dangerous than the use of an adapter because the receptacle will appear to be grounded and future owners might never be aware that their system is not grounded. If a building still uses knob-and-tube wiring, it is likely than any three-slot receptacles are ungrounded.
- removal of the ground pin from an appliance. This common procedure not only prevents grounding but also bypasses the appliance’s polarizing feature, since a de-pinned plug can be inserted into the receptacle upside-down.
Upgrading the system will bring it closer to modern safety standards, however, and this may be accomplished in the following ways:
- Install three-slot receptacles and wire them so that they’re correctly grounded.
- Install ground-fault circuit interrupters (GFCIs). These can be installed upstream or at the receptacle itself. GFCIs are an accepted replacement because they will protect against electric shocks even in the absence of grounding, but they may not protect the powered appliance. Also, GFCI-protected ungrounded receptacles may not work effectively with surge protectors. Ungrounded GFCI-protected receptacles should be identified with labels that come with the new receptacles that state: “No Equipment Ground.”
- Replace three-slot receptacles with two-slot receptacles. Two-slot receptacles correctly represent that the system is ungrounded, lessening the chance that they will be used improperly.