b1s,
I can't speak to the Tacoma plumbing codes, I'm on the other side of the country.
As to the 2nd question, I wouldn't go as far as saying it is good practice, but pex will not readily rupture when frozen like other types of water supply tubing. Depending on where it is in relation to the heated space, you might be OK just covering it with a fiberglas batt laid lengthwise over the pipe. I would like to see it in the bottom half of the total insulation blanket. If it is suspend in air, then you don't have many options. If you wrap it, when it does freeze, it will take longer to thaw. If the water isn't moving, a little bit of wrap or foam sleeve insulation could be worse than none at all.
EPM