Replacing outdoor electrical box at end of conduit

Question

Long-time lurker, first time poster. Reasonably competent DIYer, but not a licensed electrician.

I have a pair of two-outlet (1-gang) electrical boxes mounted at the top of a wooden post in my yard. One outlet pair is GFCI; the other is a plain outlet. None of the four outlets was working.

I turned off the breaker and started by replacing the two outlet pairs with known-good, weather-resistant ones (one GFCI, one plain, to match the original setup). Both outlets now work. (Evidently the problem was that the old GFCI was dead — "test" button did nothing, and "reset" button did not pop). So the wiring in the conduit seems OK.

While troubleshooting, I noticed that the boxes themselves are not in good shape. They are metal but do not appear to be outdoor grade, so they're corroded in spots, have a fair bit of debris inside, the screws attaching the boxes to the wooden post are themselves corroded, etc. Also, since they are attached to the wooden post, I'm unsure as to how to properly weatherproof this setup where each existing box is mounted to the post (the only thing I can think of would be some outdoor-grade silicone or caulk along the edges?). The setup looks like this (GFCI side shown; the box in the background contains the regular outlet):

I bought replacement covers for the fronts of the boxes, but I'm wondering if the most appropriate thing to do is replace the boxes altogether (similar to this thread, though not quite the same issue). (Note: I'm aware of the advice to just install the GFCI at the last indoor outlet on the circuit. But the relevant breaker is wired so that it covers not only the outlets on the nearby deck, but also some lights and fans — and I don't wish to spend time tracing out the topology to identify which indoor outlet is "last." I am OK with the slightly increased cost of an additional GFCI.)

3 specific questions:

1. Would it be better to replace the box cover(s), or just replace the boxes themselves?

2. If full replacement, what's the proper way to remove the old box from the top of the conduit? There are two flanged collars underneath (one on the conduit back to the house, the other presumably on the one leading to the adjacent box). But I'm having trouble unscrewing them with a wrench: they are so close together that I can't get the tip of the adjustable far enough in to get good purchase on the hex flange. I'm actually concerned that these might have been glued in place with PVC cement -- so even if I managed to grab one of the hex flanges firmly enough, I'd just break the coupler if I applied enough force. Also, they are of different sizes -- the one on the left appears to read "Cantex 5140103" (and does not look like the current version of that part), but I can't seem to get a 1-inch wrench to fit the flange, and the 1.25-inch adjustable is too bulky to fit. And the one on the right is wider (the nut might read "1 1/2," though I only see the "half" in the photo), but that thing appears to be an irregular 10- or 12-sided polygon, not a hexagon:

3. If I can manage to fish out and replace at least the run of stranded black wire from the GFCI outlet to the second outlet with solid Cu wire, does anyone know of any code issues with doing so? I was surprised to find stranded blacks here, and they're more of a pain to attach securely to the outlets than the red and white lines (which are trivially easy to mount cleanly, whether back-stab or hooked under the connection screw).

Apologies for the length of this post; hopefully I've provided enough info to clearly illustrate the problem I'm trying to solve. Thanks in advance, all, for suggestions or guidance.

-Jim

Edit (2022-11-02 23:08 CDT): Thank you, everyone, for the incredibly detailed explanations. I wish I could accept multiple posts as solutions, since I will likely try several of the ideas posted here (short term: quick paint/in-use cover; long term: taller 4x4 + extended conduit + single outdoor-rated 2-gang receptacle) — particularly those by Ecnerwal, Machavity, Harper, jay613, and George Anderson.

I mistakenly thought this would take a few hours, but unfortunately have to travel the next few days. I will post a follow-up here when I've had a chance to properly attempt the suggestions provided. Thank you again, everyone, for generously lending your expertise.

-Jim

Answer 1

So... let me suggest something more extreme: replace the whole thing. Let's look at the setup as-is

The Good

You have conduit into outdoor grade metal boxes. See the screw-top knock-outs? Those are outdoor grade. Indoor means they do nothing at all to prevent water intrusion. The wires are THWN (wet rated) as well. This is a good start and will mean you won't replace a lot of stuff.

The Bad

The boxes are old and rusty. You could try painting them to give them some more life, but they don't seem like they will work very well for much longer.

The Ugly

The reason this setup is in such bad shape is that your boxes seem to be maybe 2-3" off the ground. That means rain will hit the ground and bounce back onto (or possibly into, with an in-use cover) the box. So you're setting yourself up for failure just replacing the boxes. Exposing them to a constant stream of water is a good way to shorten their life span.

Build it right

I'd replace the 4x4. It means digging, but you'll want to update the conduit as well. I'd suggest something more reasonable like 6-12". You can then switch to a double-gang box and consolidate the two boxes in the picture.

The catch is you'll want to redo some of the conduit. And, with the wires being as they are, you'll need a junction box down low, unless you want to re-run the wires in the conduit.

If full replacement, what's the proper way to remove the old box from the top of the conduit?

So, here's what's tripping you up on this. Because those are outdoor metal boxes, they have threaded PVC connectors you screw in that are then glued to the conduit. They look like this

So you'll have to cut the PVC to get them off anyway. Either that or rip the 4x4 off and unscrew the box from the conduit (My bet is the right side is simply liquid-tight flex conduit). Hence why I say replace it.

Once you have exposed the bottom part of the conduit (by digging), use the scoring cutter (as George suggested) down there. You should have room to easily score-cut the pipe off. Then you can pull the wires out and replace the 4x4.

Now that you have a new 4x4 in place, start replacing the conduit. You'll want a box at the original height so you can nut off the wires you'll run up to the new height. Buy a metal box and attach the conduit to the bottom, then use a proper screw for pressure-treated wood to attach the box to your pole. When nutting this off, do not neglect bonding this metal box (the green screw they have in all new outdoor metal boxes). Finally, put some outdoor grade caulk along the top, to limit water running down the pole and into the box via your screw holes. You might also want to get some outdoor grade paint and add more protection for this box.

Now run conduit out of the top of this box into your double-gang. Caulk the top (where the pole is) and down the sides. Then wire your GFCI up (with your extra outlet downstream) and you should be good. Also, bond this box as well.

Answer 2

Looks like pretty typical outside work that's been in place a while.

The "right side" will probably prove to be LFNC, in a 1/2" size,

and the "left side" is probably rigid PVC-40 or -80 (should be 80) in a 1/2" size.

This type of cast box has the female threads built into the box, and very likely the adapter fitting was screwed in and the box+fitting glued to the conduit, on the left side. You'd need to release the right side and get the box off the post to be able to unscrew the left side without cutting it. The right side fitting unclamps from the liquidtight, and is then free to rotate to unscrew, once you convince it that it's really free after sitting bound together for many decades.

There's no need to replace the stranded wire. Just use a "screw-and-clamp" connection, (backwire but held by the screw, NOT "poke and pray" backwire) which almost all GFCI's have, and the "slightly better than the worst grade" and on up receptacles also have.

There's really no need to replace the boxes, either. A wire brush and a paint brush (and perhaps a new gasket, or cover and gasket) will return these to looking decent. Even not looking decent, they are not degraded to a hazardous condition as shown. If they do not have in-use covers now, add those as a functional upgrade (and current codes compliance,) plus a bit more life for the GFCI out in the weather. New screws that resist pressure-treated lumber chemical-aided corrosion would also be good.

Answer 3

Dig and see what they left you.

Harper's secret rule: they had to build it somehow.

The one on the right looks to be a union. Hold the higher nut and turn the lower. Forces are not extreme so you don't need to use "working on cars" size tools.

As for the one on the left, either they spun the box onto the fitting before nailing it to the 4x4, or there's an expansion joint vertically underground. The expansion joint usually permits rotation. It's also possible they did not cement the PVC.

They were supposed to have an expansion joint.

Answer 4

Great post! + for that. A few thoughts: Outdoor GFCIs take a beating and others here have suggested to protect the outdoor circuit with a GFCI breaker in the main panel. You don't have to do that since you've already solved your problem, just a suggestion.

Next: Hate to say it but your post looks in bad shape, seems like it's rotting at the bottom left. The electrical boxes have also obviously seen their share of wear and tear. Since your "into this project now" it might be a good time to dig things up, remove and replace the post with some good pressure treated wood, then you can kinda cheat and use a tubing cutter CAREFULLY with the wires in place, inspecting for any damage afterwards. Once you dig down enough, you should be able to spread out the conduits to make room for the cutter. I suspect that one of the conduits goes to the other outlet. If so, a complete replacement would be very simple.

Once cut and after inspecting the wires to make sure they are safe, get new boxes, couplings, male adapters, conduit, elbows etc. to reconnect everything.