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We've had loads of rain the past weekend, and now my garage has no power.

I've traced the issue to a GFCI outlet that protects the rest of the circuits in the garage - It keeps tripping.

The Power is run to the garage via an underground conduit, which I believe is standard metal electrical conduit.

I recently pulled new low voltage (ethernet) cable thru secondary conduit that was orignally for Alarm wiring purposes, and noticed that water had infiltrated that conduit. Im assuming the conduit had corroded underground.

Is it possible, if water had infiltrated the conduit that carries the garage power (120vac), that it would cause a continuous ground fault?

I've replaced the GFCI outlet it case it had gone bad, but am experiencing the same behavior.

Thanks for any ideas. I'd prefer to not have to dig up the yard to replace the conduit, but I'm guessing that's where I'm headed.

***UPDATE****

The garage did have power after the storm - at least for a couple hours. Storm ended around 7pm, and garage had power at least at 830-9pm.

Voltage Testing: Across black (line) and white (neutral) - I get 125 volts, the same I get at the breaker. Across Black and Ground (receptacle box) I get 125v

Across White and Ground, I get 0v.

I think that means I'm safe from any voltage leak. I cannot figure out why it keeps popping though. I've removed the other garage circuits, unplugged the opener and any other loads. I'm wondering if I maybe have another bad GFI outlet. –

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    I recommend using a multimeter to measure the voltage on each of the wires in the conduit at each end of the conduit and updating your question with the results. If you do this with the GFCI outlet still attached, be sure to measure on the "line" side of it. This will provide more information about any potential problems in the wiring in that conduit.
    – user4302
    Commented Jul 25, 2016 at 16:31
  • Across black (line) and white (neutral) - I get 125 volts, the same I get at the breaker. Across Black and Ground (receptacle box) I get 125v Across White and Ground, I get 0v. I think that means I'm safe from any voltage leak. I cannot figure out why it keeps popping though. I've removed the other garage circuits, unplugged the opener and any other loads. I'm wondering if I maybe have another bad GFI outlet.
    – SticklerX
    Commented Jul 25, 2016 at 17:37
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    Sounds like you should first verify that there are no flooded receptacles or junction boxes on the circuit. Excessive moisture in the wiring at joints or terminations will cause the GFCI to trip. As it is supposed to do, this is not a malfunction.
    – ArchonOSX
    Commented Jul 25, 2016 at 17:59
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    I'm assuming that the "bad" GFCI is inside the garage, not the house. In this case, current leakage inside the conduit should not trip the GFCI as it only checks circuits downstream (connected to the load terminals) as well as plugged into it. Try disconnecting the load terminals and don't plug anything in. If it still trips, the GFCI is bad. If it doesn't trip, you have a fault downstream (maybe a flooded outlet box. Do you have any outside outlets downstream?
    – DoxyLover
    Commented Jul 25, 2016 at 18:37
  • GFCIs can't detect ground faults upstream of themselves. What Doxy said, our comments overlapped. Flooded conduit is normal, that's why you use wet rated wire like THWN.
    – Harper - Reinstate Monica
    Commented Jul 25, 2016 at 18:43

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Even if the conduit is flooded, the wires should be completely insulated from any water.

I would use a voltmeter to see what is happening electrically with the wires. If the neutral or ground wires are not at zero volts, then try to determine where the bridge from a "hot" wire is. Hopefully it is in a junction box in the garage or house. You can probably narrow down the problem by temporarily disconnecting the bridged wire at one end and then the other and seeing which direction the feed is coming from.

Only if both ends are disconnected would that indicate a failure inside the conduit. Then you could try evacuating the conduit with a shop vac and see if that has an effect on the problem. If so, it is time to replace the wire inside the conduit. You need not dig it up. You ought to be able to feed a replacement wire by attaching it to the old as you pull it out. Be sure to use generous amounts of silicon lubricant so it gets easier as you go—and to make replacement easy next time. enter image description here

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