How to test electrical outlets for polarity

Updated February 21, 2017

Properly wired electrical sockets provide power without causing damage to electrical equipment. The polarity of an outlet changes when the hot and neutral connects of an outlet reverse. A reverse-polarity outlet will supply the proper power to a piece of electrical equipment, but it can damage the equipment over time. Detecting and correcting reverse-polarity outlets ensures the safety of your electronics and the efficiency of your home's electrical system.

Turn on the power to the outlet.

Plug a straight-plug outlet tester into the outlet. Check the circuit breaker or ground-fault circuit interrupter connected to an outlet if the lights on the tester do not light up when you plug in the outlet tester.

Compare the lights shining on the tester with the label indicating the functionality of the outlet. Place a piece of masking tape on the outlet if the tester indicates the outlet has reverse polarity.

Move around the area testing one plug on each outlet of your home. Mark each reverse-polarity outlet with a piece of masking tape.


Turn off the electricity when fixing reverse-polarity outlets. Hire a certified electrician to correct reverse-polarity outlets marked with masking tape if you do not feel comfortable working with electricity.

Things You'll Need

  • Straight-plug outlet tester
  • Masking tape
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