I began by removing all the pipe, the shower valve, and the bath basin fixture. I also removed the inside tambor under the sink and the middle shelf, the shelf under the basin, the bath exhaust fan, and the hot air ducts (temporarily--but they will be highly modified).
I also removed and reinstalled the electrical--bye bye Univolt, hello lightweight Intellipower. This is probably temporary, since it doesn't provide satisfactory access to the fuze panel.
I also removed the water inlet and vents for the fresh water tank. In doing so, I removed the tank drain and installed a new one with a bigger valve to allow dumping it in less than 3 hours.
Replacing the shower valve requires a special note. First, get a "shower only" valve. Otherwise, you'll have a short "down" tube for the tub outlet, which must be capped. This tube will NEVER drain, so you're always open to freeze damage. I found a Moen "shower only" valve at Home Depot. Second, this valve was originally sweated in, and I wanted to retain the through-wall fitting that the shower head hose attaches to. This required some interesting 3D juggling to get the new valve in and soldered.
The new basin faucet was a direct replacement, except it had 1/2" FIP fittings. I like these fittings--been using them for years. Easy to get a leak-free connection and they are standard if you intend to use risers. I wanted to eliminate as many connections and parts as possible, so I elected to go directly from the PEX via a swivel FIP connector. Worked great.
The hot water side was dead simple--a line from the top of the water heater around to the side wall, then along that wall to feed the basin, the shower, and the sink. The sink had 3/8" compression fittings, but there is a direct replacement to convert that to 1/2" FIP.
All lines are installed to either slope "down" gently, or lie flat on the floor. This is to promote good gravity draining of every part of the system. You can never quite gravity drain the toilet, since the valve is at the base and always has a small water column above it, up to the rim. I suppose you can open the drains and then stand on the toilet valve for a minute or two, which may be adequate, but I have a fitting that allows me to hook the air compressor to the street water inlet, and I blow everything out by opening each fixture's valve in sequence.
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