After re-connecting the lines, we turned on the main circuit breaker, then the 50A breaker at the panel, then the switch at the pedestal itself after taking the trailer off the auxiliary circuit from the garage. Everything worked!
Returning to the circuit box, Lisa tidied up the wires and tied up the pilot string, which she'll leave in place in case we get the idea of running another line. (Lisa thinks that there might be room for another 14-gauge line for one more circuit.), then (after I took this picture), sealed up the corner joint.
Lisa then went back under the house and filled in the hole from that side, and finally came outside and filled the rest of the hole. Because our soil is so sandy, she said this was relatively easy.
This has been a sort of a red-queen's race, where we've worked very hard (and spent several hundred dollars on parts) and now we're right back where we were when we started, with the 50A RV circuit in place and nothing else. However, of course we also now have the lines for a new 30A hot water heater circuit as far as the junction box and the line laid out to under the bathroom.
The next step is locating where the conduit should come up through the bathroom floor. Lisa, being worn out from the difficult work of this week, is likely to put this off until I come back from my next week's work in the Bay Area before starting that stage of the job.
While walking back from the post office this afternoon, Steve-the-plumber waved us down as we were walking past his company's Fernley office. We went inside and talked with him about the actual water heater we want to install. We've specified a Bradford-White Lowboy 30 gallon, 2-inch insulation unit with a 3000W/240V heating element. The electrical folks among you will realize that this means the circuit will draw less than half the 30A for which it will be rated. We could put a 6000W heating element in the thing if we wanted. Lisa is happier not using all of the available capacity, and the fact that the 3kW heating element means the 30 gal heater is slower to recover doesn't really trouble us. After all, we've been getting by with a slow-recovering 6-gallon water heater in the trailer for more than fifteen years and I've only managed to run out of water showering once. Besides, with water supplies being tight, we're better off doing things that encourage us to not use water prolifigately.