I hired an electrician to install a GFCI outlet outdoors. I need this to power some pumps in an aquaponics system, so I need to guarantee it works, so kids don't get hurt while playing in the water. How can I verify the electrician installed it correctly and the system is safe?

  • There should be a "test" button and a "reset". thespruce.com/test-ground-fault-interrupter-outlets-1152422 Mar 1 '21 at 17:25
  • Is that sufficient to know that in a real world situation, such as a child splashing in the water, that the electrical items installed in the water won't electrocute them?
    – Village
    Mar 1 '21 at 17:26
  • I would use a transformer in between the power and pump, or a lower voltage DC pump, if i wanted to be 100% sure.
    – dandavis
    Mar 1 '21 at 17:39
  • Well, for one thing, for the kiddos to be shocked, you'd have to have a ground fault already from one of the pumps, that alone should trip the GFCI beforehand. Sarcastically: if you really want to test the GFCI, plug in an extension cord into the gfci outlet and throw the other end in the pool (without the kiddos in it) and see what happens. Just joking of course. Seriously though, for the kiddos to get shocked, you'd need both a defective pump (IE: ground fault) AND a defective GFCI outlet. Not likely. Mar 1 '21 at 19:04

The TEST button is a pretty darn authentic test

The TEST function on a GFCI is required to create a current imbalance in the sensing toroid, exactly mimicking the action of a real ground fault. (See UL 943, clause 5.15.3 for the details.) So, you can be confident that a GFCI that trips when you push TEST will actually trip, whereas the TEST button on external testers may fail due to a receptacle being miswired in certain ways (such as Hot/Ground reverse) or a simple lack of equipment grounding provisions to the receptacle. Note that NEC 406.4(D)(2) permits the use of ground-fault circuit interrupter protection as a safety retrofit when equipment grounding is unavailable.


You can buy a receptacle tester for $10 or less, this will allow you to test the GFCI function and check that the wiring is correct. You plug it in to the outlet in question, and the indicator lights will show whether your wiring is correct or in a few common incorrect modes. The button also tests the GFCI, which should trip the outlet and force you to reset it. There's a million brands, but they all look something like this:

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A outlet tester may not identify all possible mis-wirings, but it should be enough to give you some peace of mind that the job was done correctly, and that the GFCI is functional.

  • What's the difference between that tester's button and the outlet's built-in button? Won't the built-in button not test out correctly if the three lights of that tester are not normal?
    – dandavis
    Mar 1 '21 at 17:37
  • @dandavis Theoretically, no difference between the two test buttons. However: (a) the tester lets you test at a load-side connected regular receptacle to confirm it is connected properly to the GFCI (the wires are hidden so it could be on line side and unprotected yet the GFCI itself Test would still work), (b) if the lights are not normal then the Test button may or may not work, but you'll first deal with getting the wiring straightened out so that the lights are normal. Mar 1 '21 at 18:05
  • @manassehkatz-Moving2Codidact: thanks for clarifying. Keep in mind that an outlet wired line side won't turn off when testing the gfci, so the same info is available solely from the built-in test, but i guess it's slightly more convenient to have the button and dead outlet in the same place at the same time...
    – dandavis
    Mar 1 '21 at 18:09
  • @dandavis Correct. And from a "let's be sure everything is truly safe" perspective, being able to go to the "protected receptacle" and put in a tester and confirm is more reassuring than "press the button over there and it looks like this went off". Mar 1 '21 at 18:12
  • @manassehkatz-Moving2Codidact To the view of the OP, should this tester's button really provide any additional peace of mind though? That's the part I don't like; if they are the same test, this is just a false hope and sense of security; safety theatre.
    – dandavis
    Mar 1 '21 at 18:14

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