The more the merrier? (I think not in this case...)
I got my pipes thawed last night, for fun I guess. Then I just turned the water back off and opened the tap since I don't have a plan for keeping them unfrozen yet. I might just leave them like that through the weekend when it's supposed to warm a little. Fortunately it seldom gets this cold here for this long. Unfortunately, occassional days this cold aren't all that unusual.
I actually have one of those heat guns, been having some fun with it.
The house is 100 years old and there's no insulation at all in the basement (plumbing is a year old, why they ran it right up the brick beats me!). The basement in general is lower to mid 50s, the brick the pipe runs up was about 37 when I measured it, there is a gap at the very top of the brick that feels colder. The brick about 2 feet away measured at 27. Inside the bathroom, the drywall on the lower half of the wall is cold to the touch. I pulled the plastic doo-dad where the pipe comes through the wall away and tried to measure the temp behind the drywall. I was getting right around 32.
Clearly I need to insulate the basement! But as for this particular pipe, I could maybe get something 1/8" thick behind it. Perhaps a sheet of craft foam or the fabric insulation that goes in pot holders would fit.
It looks like I could get heat tape with a thermostat that would be safe for PVC pipes, but I'd have to install a new electrical outlet to use it.