My girlfriend recently moved into a new apartment which I have come to suspect might have bootleg grounds, or otherwise improperly wired outlets. After multiple surge-protectors said that they were not grounded she bought a GFCI/outlet tester. When plugged in the tester says that the outlets are wired correctly, but when the GFCI test button is pressed the GFCI doesn't trip and the tester changes to reading that hot and neutral are reversed until the GFCI test button is released again. Pressing the test button on the outlet itself works normally. None of the outlets have any special labels.

The building is old, and originally did not contain apartments, so it seems reasonable to assume that the wiring was in some way retrofitted into it. Some searching around on the internet has led me to suspect that these things might be symptomatic of the outlets having a bootleg ground. Is this the correct conclusion, or are there other possible causes of this?

  • Could you open up one of these GFCI's and take a few pictures of the wiring and connections? When you say the building is old, do you know about how old? Aug 30, 2017 at 19:50
  • I'm diagnosing things remotely (the new apartment is the result of a recent cross-country move), but I'll see if I can walk her through opening one up to get some pictures. I don't know exactly how old, but I'd guess in the 50–70 year old range.
    – Nyle
    Aug 30, 2017 at 20:35
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    I wouldn't bother, I'd just build the cheater tester I describe and mail it to her. Easier to unfurl some wire and stick an alligator clip on a grounding electrode, than open up a receptacle... Especially because the landlord may not approve of the latter! Aug 30, 2017 at 20:57

1 Answer 1


It is normal for a plug-in GFCI tester to not work, if the receptacle is not grounded. GFCI testers are not magic.

GFCIs work by comparing current on the "hot" wire to current returning on the "neutral" wire. If all is well, they should be equal. if they are not equal, some current is traveling down a third path possibly through a human.

If a third path does not exist, then tripping a GFCI is impossible. An external tester cannot trip a GFCI if it only has access to hot and neutral. The GFCI itself can test itself by using an internal path which goes around the LINE and LOAD terminals, both of which it has access to. An external tester can't do that.

So failure to trip at a downstream outlet does not tell you anything one way or the other about whether ground has been bootlegged there. It only tells you ground is not present. Such a receptacle should have "GFCI protected" and "No Equipment Ground" stickers and will need those to pass home inspection.

To use an external tester at such a location, get a common 3 to 2 prong cheater, the kind that has a 3 inch green pigtail meant to be attached to the receptacle screw. Extend that using whatever wire you have on hand, all the way to the panel, attach it to the building's grounding electrode system. That becomes the third path.

You are allowed to retrofit proper grounds to a receptacle without disturbing the hot/neutral wiring, and you don't even need to use the same route. (Also remember metal conduit is a ground path). However if a circuit has GFCI protection upstream, I would call such an upgrade a low priority. In some ways, GFCI protects better than actual grounding.

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    If it is the case that the receptacles are not grounded (and are just missing the mandatory stickers), wouldn't the outlet tester have found that the outlet has an open ground? When it was tested it read as being a properly connected outlet.
    – Nyle
    Aug 30, 2017 at 21:19
  • @Nyle -- it could be that the ground connection is sloppy/faulty Aug 30, 2017 at 22:23
  • @Nyle good point, that would suggest a bootleg ground or a broken GFCI. Correct indication on an ungrounded outlet is 1 light (open ground). However even if they bootlegged ground, that's not an urgent matter as long as the GFCI protection works. Aug 30, 2017 at 23:52
  • @Nyle rethinking, the red light proves not bootleg groung Aug 31, 2017 at 12:45
  • as I was saying, ground. The red neon light is across neutral and ground. GFCI test places a resistance across hot and ground. If ground is floating, the resistance and neon light are now in series. The second yellow (H-G) was never on at normal brightness, that's just bleedover from the other neon. See that all the time. Aug 31, 2017 at 12:54

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