A GFCI plug can look perfectly fine and still not work. The only way to know it will protect you is to test it. The good news: it takes about 30 seconds and needs no tools.
How to test a GFCI plug
- Plug it into a live outlet. The indicator light should come on. If it doesn't, check that the outlet has power by plugging in something else.
- Press TEST. You should hear a click, the indicator should change, and power to the equipment should cut off. If the equipment was running, it should stop.
- Press RESET. Power should return and the indicator should come back on.
That's it. If all three happen, your GFCI is working.
If pressing TEST does not cut the power, stop using it. A GFCI that doesn't trip on TEST may not trip during a real fault either.
How often should you test?
- Monthly for anything you use regularly, such as pool and spa pumps during the season
- Before each use for tools that sit in storage, like a pressure washer you use a few times a year
- After any event such as the plug getting soaked, dropped, or run over
Many modern GFCIs also monitor themselves internally, but that's a backup, not a replacement for the button test. The TEST button checks the whole tripping mechanism, start to finish.
Can I use a plug-in outlet tester?
Those small three-light testers with a GFCI button are made for outlets. A GFCI plug on the end of a tool cord has no outlet to plug a tester into, so use the built-in TEST button instead.
The exception is a GFCI extension cord with outlets on the end. You can plug a tester into one of its outlets and use the tester's GFCI button as a second check.
Signs it's time to replace your GFCI plug
Replace the plug if any of these are true:
- TEST doesn't cut power. This is the most important one.
- It won't reset on a live outlet, even with the equipment switched off. Many modern GFCIs refuse to reset once their internal self-check finds a problem.
- It trips with nothing running. If it trips with the tool switched off and the cord dry, the GFCI itself may be failing.
- Physical damage: cracks in the housing, a loose back cover, a worn or missing gasket, or bent prongs.
- Heat damage: discoloration, melting, or a burnt smell.
- Water inside the housing that doesn't go away after drying.
- Buttons that stick or feel loose.
When it's not the plug
If the GFCI tests fine but trips every time you turn your equipment on, the GFCI is probably doing its job. Something in the equipment, such as a damaged cord or moisture in the motor, is leaking current. Replacing the plug won't fix that. Get the equipment repaired.
More troubleshooting: Pressure Washer GFCI Won't Reset? and Why Does My GFCI Plug Keep Tripping?
Replacing a failed GFCI plug
If your GFCI fails the test, you usually don't need to replace the whole tool or pump, just the plug. On any 120V, 15A-or-less device with a 3-wire cord, a replacement plug installs with a screwdriver in a few minutes.
- For pumps and equipment that run unattended: Kaper Auto-Reset GFCI Replacement Plug
- For pressure washers and hand-held tools: Kaper Manual-Reset GFCI Replacement Plug
- No wiring at all: Kaper 3 ft GFCI Extension Cord
Not sure which one? See Auto-Reset vs. Manual-Reset GFCI Plug.
A GFCI reduces the risk of electric shock but does not replace safe work practices. If you're not comfortable working with electrical wiring, consult a licensed electrician.