How do I add water resistance in RMC

How can you splice into existing underground rigid metal pipes underground and hide the junction box?

There are no scenarios where you can reuse the THWN wire that is now on the line. It is just too short as, as you say, it is spliced ​​as soon as you enter the house.

Trying to set up a splice point at the old location is quite difficult and not useful given the low cost of the wire. Since you want to go the last 10 feet in direct ground wire, you need to bury at 24 "which actually means 14 'and the descent to 2' depth on either end also needs to be just as physical wire protection in the line. Saying that this is inadequate is an understatement, and I think it will cost you more than a new wire pull all the way.

The easy way

This doesn't seem to be the easy way to go. But that's just because they are handicrafts that you are unfamiliar or unfamiliar with.

The long length of the rigid pipe is not wasted and the additional distance to the garage is not increased. Enter the garage in the normal way (on the building side, then through an LB conduit body). Then run a new THWN wire through. dead easy.

Dig up the area under the old junction box. Go as deep as necessary to expose the old rigid pipe. Remove the old 90 degrees that run the pipe up and if there is an angle you can cut off a lot of it instead of digging more dirt to swing it. Leave enough meat on it to have a pipe wrench to unscrew from the coupling.

From there, dig a little in the direction you want the pipe to go. When the wires are gone you can stick a piece of post rod in it to confirm the direction. Plan where to take a 45 or 90 turn (45 is better) to get to the garage. This is metal tubing that requires you to cut and thread a pipe for, but all you need to do is dig 8 "(to get 6" cover).

You will need a 10 'stick of rigid, a 90' elbow, and possibly a 45. Possibly a nipple or other stick. Rigid is expensive, but this little piece is cheap. This allows you to use 2xTHWN-2 instead of expensive UF.

It's good to either have a pipe vise and RiDgid threader, or do a few runs to the hardware store to thread the pipe to length ... the last one is a bit critical though if you're approaching the wall at an angle, who allows it to make it less critical. Do not select the point of passage until the pipelines have reached it. And don't stand on a beam.

It's a lot of work, but it's also 90% of the work. Lock inside in a steel junction box. Now you pull out a black and white THWN-2 and you're done. Very easy pulling, especially with stranded THWN. Peel the bottom off the metal box.

And you have expansion space to blow it out to a MWBC (another wire) or even pull a bigger wire for a subpanel.

The hard way

You can essentially use the rigid cable as a wire protector (not a proper cable). However, this means that you run the UF continuously from the house to the garage and pull the cord through the long cord, which is the mark of the amateur. You can now no longer reuse a THWN cable in the line.

You will need to extend the rigid down to a depth of 25 inches to allow the direct ground wire to exit the conduit at a depth that it will allow

  • Dig back the 10 to 20 feet of existing rigid pipe so you can bend it down so that its exit is at a depth of 25 inches for 24 inches of coverage.
  • Add two 90s and a nipple to make the rigid fall straight down. That means at least three 90s on that move, however, which makes it a challenge.
  • Add two 45s and one longer nipple which will solve the drag problem, but will get you much closer to the garage and almost ruin the purpose of not just doing it the easy way (what's that purpose anyway?).

Then dig at 25 "to the garage where you need to use more wire (90 and stick and LB) as protection / protection to protect the UF when it rises from 25" and then come up the side of the garage an LB pipe body and further into the garage.

So you still need a whole bunch of wires and more of the weird parts ... and you can only walk a few feet in the open dirt. You have to really like digging to use this option.

Worse, you made the customer far worse off than the other option. This only provides a single circuit # 12 and can never be updated. If he ever wants more power in the garage, he probably isn't aware that he could just dig in the right place and put in the missing 6 to 7 feet of line and have the right line all the way. Without knowing it, he would just dig up a completely new cable.

In all fairness, this option just seems stupid.