Heard a noise at 2:30am, thought it might be a rat or a coyote bumping his head under the RV. Got up and stepped in a puddle right under the fridge area. Went out and shut off the water supply... back to bed.
Next morning I did some investigating and found a broken 3 way valve near the water heater. This was under a pantry cabinet and in a very tight space. After doing some reading on this forum, I see that this piece is part of the winterization process, though I'm pretty sure the previous owner, my Dad, never touched this in its 20 year history.
Went down to the local RV store and picked up the new $14.99 Flair-It 3 way valve and after a very tight squeeze and lots of cussing, installed it and turned the water back on. While I was in there I shortened one of the hoses so as not to keep the badly squeezed in piping, causing extra pressure. So far so good! I can see a need to keep an eye on this area as all of these old and brittle pipes are in the same condition.