How to Connect an Additional Outlet to an Existing Outdoor Outlet

17 December 2015
 Categories: , Blog


If you have problems reaching the outdoor electrical outlet when you are hanging your Christmas lights, there is a simple solution. You can wire an additional outlet from the existing outlet.

Your existing outdoor outlet should be a GFCI (Ground Fault Circuit Interrupter) outlet, which shuts down when it detects insufficient grounding from wet or damp conditions. Luckily, if you wire an additional outlet from a GFCI outlet, the added outlet is also protected, so you only need to install a less expensive standard outlet.

What You Will Need for This Task

  • A weatherproof single gang box: This is the box that holds the outlet. 
  • A gang box cover: You'll want one that flips down to protect the outlet from weather. You may choose to buy a gang box with an attached cover or a separate cover.
  • 1/2" EMT conduit: This is the metal tubing through which your wire will run. You will need to measure the distance from your existing outlet to the location of the new outlet to determine the length needed. It is usually found in eight and ten foot lengths.
  • 1/2" conduit box connectors and couplings: The connectors connect the conduit to the gang boxes while the couplings connect lengths of conduit together. if the distance between the outlets is less than one length of conduit, no couplings and only two connectors will be needed.
  • 1/2" conduit straps: These are used to hold the conduit against the wall.
  • Wire: You will need a sufficient length of wire to reach both outlet, with an additional few feet for connection purposes. Check the breaker that controls the existing outlet. If it is a fifteen-amp breaker (the number is stamped on the breaker), you will need a fourteen-gauge three wire sheath, and for a twenty amp breaker, you will need a twelve-gauge three wire sheath.
  • Wire cutter/stripper
  • Hacksaw: Or you may use a similar item capable of cutting conduit
  • Cordless drill with screw chuck
  • Philips head screwdriver

Accessing the Existing Outlet

Turn off the breaker that supplies the existing outlet, and remove the connecting screws that hold the outlet in place. You may need to remove the flip down cover first. Pull the outlet from the gang box.

When the outlet is removed from the gang box, punch out a pre-scored knockout hole for your conduit and twist a conduit connector into the hole.

Installing the New Outlet

Knock out a pre-scored punch out in the bottom of the new gang box and screw it onto the wall in the proposed location. Twist a conduit connector into the punch out hole. 

Cut the conduit to length and slide it into the connector on the new gang box, tightening the screws to secure it. Start to feed your wire sheath into the new gang box and through the conduit until it reaches the end. If multiple lengths of conduit are needed, connect them with couplings, feeding the wire sheath through each length before adding another.

As conduit is added, secure it to the wall with conduit straps, which have openings for one screw on each side.

When you reach the existing gang box with the conduit, slip it into the connector and tighten the connecting screws. Feed the wire sheath into the existing gang box, allowing several inches to hang from the box.

Connecting the Wires

You will use your wire stripper tool to strip one inch of insulation from each of the three wires in the wire sheath. The black wire will be looped around the gold "line" terminal at the bottom of the existing GFCI outlet, while the white wire will be looped around the silver "line" terminal at the bottom of the outlet.

The green or copper colored ground wire will be looped around the green grounding screw in the gang box. The outlet will then be pushed back into the gang box and secured with the connecting screws. Replace the cover, if needed.

You will next cut the wire sheath at the new gang box, leaving several inches outside the box. Strip the wires as before, and connect the black wire to the upper gold terminal, the white wire to the upper silver terminal, and the green or copper wire to the green grounding screw.

Push the outlet into the gang box, and secure it with the connecting screws, then connect the cover according to the instructions provided with the selected model.

Turn on the breaker and say goodbye to your extension cords, because you're ready to decorate. However, if you find this task overwhelming, consider calling in an electrician, such as JF Electrical Contractors, Inc., to install the outlet safely and efficiently.