Back during the blizzard of '78 my brother, who owns a welding fab/repair shop, and I wore out a Miller Roughneck portable welder thawing water lines on farms. The pipes don't actually get hot to the touch.
The dumb thing was, when it started warming up for a few days folks would stop letting their water trickle and when the frost line came back up they'd freeze all over again! Thawed the same lines 2 or 3 times that winter. We always made sure they unplugged all appliances before we started.
