First post on this board, so I guess I should introduce myself.
I'm a fairly handy guy. I've done construction before, and can do plumbing, electrical, sheetrock (but not particularly well) and lots of other things. I'm Air Force, and have a particular job that reinforces the fact that I'm fairly mechanically inclined. When my wife and I moved out to Utah, we bought an older place (built 1972) instead of renting--it's a two-story with the basement 1/2 below grade, and the second story soffit is about 4' above grade. Tom Hanks and Shelley Long haven't shown up yet, but I reckon it's just a matter of time. :D
First work we did on the place was to gut the upstairs bathroom and refinish it. With studs exposed, I can see where previous owners 'Frankenstiened' together plumbing, to go from copper, to PEX, to copper again, and back to PEX . . . all on the same run of water line. They ran hot/cold PEX between floor joists, out a soffit & up an exterior wall, then back into an interior wall to the shower valve of the upstairs bathroom. We hadn't used this bathroom when we moved in because the plastic surround was cracked, so we simply used the downstairs bathroom. This is the first winter we've had the upstairs finished, and have been using the bathroom, so we never had any idea things were wrong with the house. We've since torn out the downstairs bath, to get that moving along as well.
The past few weeks, we had a cold snap and some minor freezing in the PEX lines, that cut off water to the upstairs bathroom. I've insulated underneath and 'outboard' of the PEX lines as best I could from the cold, but on occasion, it will still take 5 minutes of a hair dryer from inside the house to warm them up enough so they flow.
I don't want to close up the walls without figuring something out, or leaving a bigger problem for later. The upstairs shower's already tiled (did that when it was warmer, before this was a known problem). Any ideas or suggestions while I still 'have time'? :D