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Reuben Saltzman

Ungrounded Three Prong Outlets – How To Fix

One of the most common electrical defects that I find when inspecting old houses in the Twin Cities is ungrounded three-prong outlets.  This happens when a standard three-prong outlet is wired without the ground wire being connected.   Today I’ll give a brief explanation of what the third prong is for, and I’ll discuss a few ways to correct a miswired three-prong outlet.  I didn’t consult an attorney before writing this article, so I feel like I should add a disclaimer before giving any electrical how-to advice: Don’t do any of this work if you’re not qualified.  This is only an overview.

The third prong on an outlet is commonly referred to as ‘the ground’, and it provides an alternate path for electricity that may stray from an appliance or product.  This is an important safety feature that has been required since 1962, which minimizes the risk of electric shock, and allows surge protectors to protect your electrical equipment, such as televisions, computers, stereos, and other devices.

The ideal way to repair an ungrounded three-prong outlet is to establish a continuous electrical path back to the main panel.  If the outlet is installed in a metal box, and that metal box has metal conduit all the way back to the panel, this will probably be pretty easy to do.  To test this, you can use an inexpensive pig-tail electrical tester.  With the circuit energized, touch one end of the tester to the hot wire, which should go to the smaller slot on the outlet, and one end of the tester to the electrical box  (see the first photo below).  If the tester lights up, the box is grounded.  Now all you need to do is attach a bare copper wire to the box, and use this as the ground wire for a three-prong outlet (see lower photo below).

Testing For Ground on a Two-Prong Outlet Grounding a three-prong outlet to a box

Note: if the electrical box is installed in a concrete block wall, this will provide a ground path for the outlet box, telling the tester the box is grounded.  This is not a proper ground path for the outlet. If there are outlets installed in a concrete block wall, my advice would be to bring in an electrician to get to the bottom of how to properly ground the outlets.

If you perform the test with a pig-tail tester and the light doesn’t light up when you touch the hot wire to the box, the box is not grounded (or you’re not touching a hot wire).  In this case, you could run a ground wire back to the panel, or you could install a GFCI outlet.  A GFCI outlet provides protection against lethal shocks, but without a ground wire, this outlet will not provide any protection for your electrical equipment.  A surge protector plugged into an ungrounded outlet will do nothing, and you could fry your new plasma TV.  You will need to add a sticker to the GFCI outlet that reads “No Equipment Ground” – this sticker comes with every GFCI outlet.

Reuben Saltzman, Structure Tech Home Inspections – EmailTwin Cities Home Inspector

40 responses to “Ungrounded Three Prong Outlets – How To Fix”

  1. tina
    May 8, 2009, 2:02 am

    wat i used to think that the third wire is useless, its just a fancy feature, which actually does not do any thing, but after reading this i am amazed how imp it is.

  2. eric
    June 22, 2009, 6:02 am

    Does anyone know if the gfi built into an a/c unit good enough or do I need to put in a real gfi in the wall?

  3. Reuben Saltzman
    June 22, 2009, 8:03 pm

    The built-in GFI on an AC unit will protect the AC unit the same way that a GFCI outlet would.

  4. Reuben Collins
    October 12, 2009, 1:19 pm

    I was under the impression that the tabs & mounting screws on an outlet were connected to the grounding screw on the outlet. So if the metal conduit is providing the ground, if you’ve securely screwed the outlet into the metal box, it’s grounded in a round-about way. Not true?

  5. Reuben Saltzman
    October 12, 2009, 4:39 pm

    Reuben – it depends on the outlet. A self-grounding outlet will do exactly what you’re talking about, but most outlets are not self grounding. The next time you’re at a home improvement store / hardware store, check out the outlets. You’ll notice that the self-grounding outlets cost a little more, and have a little more metal in the frame that ‘bonds’ everything together.

  6. Reuben Collins
    October 15, 2009, 8:43 am

    well shiz. I’ve been doin’ it wrong…

  7. Top Ten Home Inspection Defects For Old Houses | Reuben's Home Inspection Blog
    November 2, 2009, 7:54 pm

    […]  Improperly Wired Outlets Ungrounded three-prong outlets and outlets with reversed polarityare very common defects.  These are shock hazards.  You can […]

  8. peter
    April 15, 2010, 11:02 am

    my outlets are not grounded and running the ground back to the panel isn’t possible right now (financially). and since you mentioned plugging a surge protector into an ungrounded outlet will be useless, i wanted to know if I could use a UPS back up with my ungrounded outlet. I would like to plug the UPS into the ungrounded outlet, then a surge protector into the UPS, and my TV/PC into the surge protector. Will this help against frying my electronics?

  9. Reuben Saltzman
    April 15, 2010, 4:37 pm

    Hi Peter,

    That’s beyond the scope of my knowledge. That sounds like a great idea… from what I know about UPS devices, all the power actually comes directly from the battery, and the battery just gets continually charged. I ‘m not sure if that would protect you from surges. I can tell you that adding the surge protector would certainly be useless – this would just be an expensive power strip.

  10. Tony
    November 19, 2010, 9:05 pm

    Hi there i just read your post on this and i had question i recently bought a old house. and i did not notes this when i bought it. but someone had grounded one outlet to a grounding rod. should i unhook this or is it safe as is. the ground seams to function as none of my surge protectors say its ungrounded. so though i would ask here thanks have a great day.

  11. Reuben Saltzman
    November 20, 2010, 6:03 am

    Hi Tony, I’d have to say I really don’t know. I’m sure it would be better to have it grounded back to the main panel, but for a long time it was standard practice to ground subpanels only using a driven ground rod.

  12. Tony
    November 22, 2010, 9:05 pm

    thanks for getting back to me the house was built in 1942 the wire looks pretty old i wonder if it is best to leave it as is. anyhow thanks for getting back to me have a great day.

  13. Brad
    December 11, 2010, 7:27 am

    Several of the 3-prong outlets in a home we are looking to buy are not grounded. Also, there is unprotected romex wiring in a bedroom closet on the first floor. The house is otherwise immaculate. Is this a sign of a bigger electrical problem? or an easy fix?

  14. Reuben Saltzman
    December 11, 2010, 1:33 pm

    Brad – ungrounded three-prong outlets are certainly a sign of amateur workmanship, but not necessarily a sign of bigger or other electrical problems.

    Sorry, but without having inspected the house you’re talking about, I can’t tell you how easy it would be to fix this.

  15. Jack
    July 29, 2011, 5:55 pm

    Thanks for the info. I have several of these in my old house. I presume it’s acceptable to simply change them to two prong outlets, correct? Grounding them is not practical and GFIs all over the house is expensive overkill for lamp circuits. I presume codes don’t require you to provide grounded outlets in all old work.

  16. Reuben Saltzman
    July 29, 2011, 7:10 pm

    Jack – yes, changing them back to two-prong outlets is ok. It’s not the preferred method… but it’s legal.

  17. Mike Collins
    August 6, 2011, 6:51 am

    Hi Reuben, I have a house with a jacuzzi tub. the tub is plugged into an ungrounded outlet, however it comes out of a GFI breaker. Is this adequate protection? Thank You

  18. Reuben Saltzman
    August 7, 2011, 6:48 am

    Mike – ‘adequate protection’ could be interpreted different ways. The GFI circuit breaker should be enough to protect you from a lethal shock… but this wouldn’t provide any type of protection for the equipment.

  19. Verne
    July 12, 2012, 11:34 pm

    Who do I contact to get my outlets grounded?

  20. Reuben Saltzman
    July 13, 2012, 3:30 am

    Verne – a licensed electrician.

  21. Aaron Klob
    September 7, 2012, 4:08 pm

    I’ve been doing it wrong as well. Uh-oh. Our house was built in exactly 1962. Would there be a ground wire to the panel? We just had our panel replaced a couple years ago. And I used a tester on our outlets In order to see whether they were grounded our not, and about 80% of our house outlets show grounded, and when we upgraded some of those outlets to three prong and I didn’t ever see or use a ground and most of those outlets show as grounded, maybe the outlet boxes are grounded and when the outlet is screwed on to the box, it probably grounds it. But what doesn’t make sense to me, is that some outlets aren’t grounded and they are three prong plug outlets that I put in. That’s odd, the ground must be broken somehow on those outlet boxes. Is there a quick fix to this?

  22. Reuben Saltzman
    September 16, 2012, 7:48 pm

    Hi Aaron,

    If I were you, I’d do a little further testing to make sure the outlet boxes are truly grounded. You can figure this out by using a pigtail tester like I show in the photos. If the boxes aren’t grounded, there is probably no quick fix.

    I think it would be well worth your money to have an electrician or home inspector come out to give you a better idea of exactly why some outlets are grounded and others aren’t. Without seeing them, I hesitate to guess at it.

    – Reuben

  23. Ben
    November 29, 2012, 11:21 pm

    Hi, I have one receptacle recently added by a general contractor and he said it is a self grounding box, but when i plug my surge protector in ,the light shows that it is unground. The receptacle itself has a green light says that surge protected tho. Is it safe?

  24. Reuben Saltzman
    November 30, 2012, 4:38 am

    Ben – perhaps the contractor meant to say it’s a self grounding ‘outlet’ ? If you plug your surge protector in and it shows the outlet is not grounded, it probably isn’t. Stop by a hardware store or home improvement store and pick up a three-prong outlet tester to double check. They cost less than five dollars.

    Also, double check your outlet – are you sure it has a green light indicating it’s surge protected, or is it GFCI protected?

  25. Bill
    March 4, 2013, 5:11 pm

    I have and old home. Can I put gfci in all the hose.no ground. Thank you.

  26. More interesting facts about wires. Or, procrastinating while studying physics. | Information
    March 16, 2013, 3:19 pm

    […] newer outlets have the extra hole and are supposed to be grounded (however, sometimes they actually aren’t.) Basically, that extra prong/hole contains a ground wire which connects to the ground. Its purpose […]

  27. amy
    April 24, 2013, 10:30 am

    I have two fuse boxes, one at the main and one in a bedroom. 3/4 of the house receptacles (1951) is without a ground. 1/4 is grounded (1964) addition. I have brought a ground wire to each ungrounded receptacle. The bedroom fuse box is the source for these receptacles. What do I connect the ground wire from the receptacles to? Do I need to somehow ground the bedroom fuse box and if so to what? The hot and cold water and gas lines are bonded. I can not locate a ground rod, should I just add one for precaution? Thanks in advance.

  28. Reuben Saltzman
    April 24, 2013, 1:07 pm

    The ground wires from the receptacles would get grounded to the fuse box. The fuse box should already be grounded to the main panel. If it’s not, this is a safety hazard that should be corrected.

  29. Eric
    May 3, 2013, 4:19 pm

    This was a very useful article. If I have a digital multimeter, can I use that instead of the pig-tail tester? So if I get a reading of 120v if I contact both outlet slots with the multimeter probes and then get the same reading if I touch one probe to the hot wire and the other probe to the metal box, does the mean the box is grounded?

  30. Eric
    May 3, 2013, 7:39 pm

    Great article! If I have a digital multimeter can I use that instead of the pig-tail electrical tester? So if I put the prongs into the 2 outlet openings and get 120v and then put them to the hot wire and the metal box and get 120v that means the box is grounded?

  31. Reuben Saltzman
    May 3, 2013, 7:43 pm

    Hi Eric, yes and yes.

  32. Kristi Gonce
    August 5, 2013, 9:55 am

    Hi Eric, I have what I consider to be A large emergency. I recently purchased a window unit AC that had a built in GF I in the cord. it worked great except for a few times that the gfi flipped but i just checked the unit & turned it back on via the gfi button. this morning I noticed it was not on so I went to reset it as usual & it will not work. the gfi just comes back out when pushed in. I’ve also tried connecting it to a different wall outlet with no luck either. do you have any suggestions??? IM DESPERATE & BURNING UP!!!!

  33. aka: Jimmy Burke
    September 5, 2013, 10:45 pm

    Great page. You tell it how it should be told. There are so many home inspectors that will state that it is usually acceptable to install GFCI outlets in place of non-grounded outlets. This less expensive fix appeases the realtors. I have been a successful home inspector for 7 years. However, sadly I am getting out. Can’t take being a thorough inspector in Pennsylvania anymore. But at least I see from your professionalism and knowledge at least there are some good inspectors and some good states to be a home inspector. Great web-page

  34. Nick
    October 15, 2013, 12:16 pm

    Question…

    If you have three prong outlets and find the metal box isn’t grounded (or have no metal box) are you capable of protecting your electronics by installing self grounded GFCI outlets and a whole home surge protector?

    Thanks,
    Nick

  35. Reuben Saltzman
    October 15, 2013, 12:23 pm

    Hi Nick,

    I can’t recall ever seeing a self-grounding GFCI outlet, and even if there is such a device, it would only work with a grounded box. Installing a GFCI outlet will give protection against being electrocuted, but won’t do anything for your electronics. I would imagine that a whole-home surge protector would help to protect your electronics, but I’ve never dug into that topic. That might make for a good future blog post.

  36. Nick
    October 15, 2013, 12:43 pm

    Reuben,

    Thanks, I may be misunderstanding. Let me rephrase. If you have three prong outlets and find them ungrounded either because the metal box isn’t grounded (or have no metal box), are you capable of installing self grounding outlets while being capable of utilizing a surge protector at that outlet to protect electronics? If not, would a whole home surge protector at the box take care of the problem?

  37. Reuben Saltzman
    October 15, 2013, 12:47 pm

    If you have three prong outlets and find them ungrounded either because the metal box isn’t grounded (or have no metal box), are you capable of installing self grounding outlets while being capable of utilizing a surge protector at that outlet to protect electronics?

    No.

    If not, would a whole home surge protector at the box take care of the problem?

    I don’t know.

  38. Nick
    October 15, 2013, 1:24 pm

    Thanks Reuben! I’ll do a bit more digging into whether a whole home surge protector would remedy appliance protection while plugged into a self grounded electrical outlet… However, a future blog may do the trick.. 😉

    Thanks again,
    Nick

  39. David
    January 3, 2014, 8:15 pm

    Reuben,

    I am having trouble determining if my metal outlet boxes are grounded or not. If I add a ground wire to the box, could that possibly be a solution? My house was built in 1958. These outlets were two prong and I have just replaced them with three prong, hoping that the boxes were grounded.

  40. Reuben Saltzman
    January 4, 2014, 6:49 am

    @David – please read the third and fourth paragraphs in this blog post.

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