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How to replace a two-prong outlet with a grounded three-prong outlet?

Learn how to safely upgrade your outdated two-prong outlet to a grounded three-prong outlet with easy-to-follow steps, essential tips, and important safety advice.

Reviewed by Content Team

Head of Content, D. Gorenko

Updated June, 5

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How to replace a two-prong outlet with a grounded three-prong outlet?

 

Understand the Importance of Grounding

 

Before you start replacing your old two-prong outlet with a grounded three-prong outlet, it’s important to understand why grounding matters. Properly grounded outlets help prevent electrical shocks and protect sensitive electronics and appliances from electrical surges by providing a safe pathway for electricity. Older homes, such as those found frequently in St Louis and Nashville, often feature two-pronged outlets, which lack a grounding wire and therefore present certain electrical risks.

 

Determine If Ground Wire is Present

 

Carefully turn off the power to the outlet you will be working on at your home's electrical panel or fuse box; make sure to verify the power is off with a voltage tester. Next, remove the outlet cover and carefully unscrew and pull out the outlet from the electrical box. Take note of the wiring behind. In some cases, even if the outlet is two-pronged, you might find a grounding wire (usually a bare copper or green insulated wire) tucked away unused in the box. If you do see this wire or a metal conduit box, your circuit may already be suitable for a simple swap to a three-prong grounded outlet.

 

If Ground Wire Exists—Installation Procedure

 

If you find a grounding source (bare copper wire or conduit) in the electrical box, your installation procedure is straightforward:

  • Turn off electrical power to this circuit at the breaker panel and double-check with a voltage tester.
  • Unscrew the terminal screws of the old outlet and disconnect the wires from the terminals.
  • Connect the black wire (hot) to the brass-colored terminal screw on your new three-prong outlet.
  • Connect the white wire (neutral) to the silver-colored terminal screw on the outlet.
  • Connect the grounding wire (bare copper or green insulated) or the grounding pigtail from the metal box to the green grounding screw on the outlet.
  • Tighten screws securely and carefully fold wire connections into the box as you install the new outlet.
  • Verify connections are correct and replace the outlet into the box, securing it with the screws provided.
  • Replace the cover plate, restore power from your circuit breaker, and test with an outlet tester to ensure proper wiring.

 

If No Ground Wire Exists—Appropriate Next Steps

 

If you discover no ground wire exists, you have a few options to safely install a three-prong outlet:

  • Add Grounding Wiring:

    Have a trained professional electrician run a new ground wire to your outlet box, connecting it back to the electrical panel or proper grounding rod. This ensures maximum safety and compliance with modern electrical codes.
  • Install Ground Fault Circuit Interrupters (GFCIs):

    GFCIs provide protection from electric shock by detecting discrepancies in current flow. While they don't provide an actual grounding connection, they enhance safety and are code-approved for replacing two-prong outlets without grounding. Label the outlet clearly as "No Equipment Ground" (labels often come with the GFCI device).
  • Rewiring House Circuits:

    As an ideal, long-term solution, rewiring older homes with updated grounded wiring might be necessary, particularly in historic neighborhoods common in areas like St Louis or Nashville. This approach adds safety and increases property value effectively.

 

Testing and Ensuring Proper Functionality

 

Once installation is complete, use a receptacle tester to confirm the outlet is correctly wired and safely grounded (or appropriately labeled if installing a GFCI without an actual ground). The tester will clearly display if there's reversed wiring, open grounds, or other errors. If any problems arise, double-check connections or contact a qualified electrician for assurance and professional advice.

 

Important Safety Reminder

 

If at any point you’re uncomfortable working with electrical wiring or uncertain about conducting these steps safely and correctly, it's important to contact a licensed electrician. Electrical work poses serious risks, and professional electricians have the expertise and equipment to perform installations safely, adhering strictly to current electrical codes and standards, thus ensuring your home remains safe and compliant.

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