They use an arc welder and step up transformer called the Harold Electric Pipe Thawer
They connect to a house water pipe.
They connect to a pipe in the street.
Then they pump between 200 and 350 Amps through your pipes to get them hot!!
Hot enough to steam. Hours later the ice melts and water begins to flow.
I learned from Rob that Ouray has no water meters, yes that's right a flat rate for water. That being the case, let those facets flow!!
I also learned that Ouray has no water pumps, the city is entirely gravity fed with pressures
running between 130 and 200 psi. Just enough to get water around town.
Well after 5 hours at 200+ amps, no water. At 9PM, Rob and Harry went home.
I survived by melting snow. You know how long it takes to melt snow? At least 15 minutes per pan.
They returned the next morning bright and early with more tools.
Here they're digging up the main to clamp directly to my frozen pipe.
The frozen dirt road is like concrete, they estimate 2 hours to dig down 2 feet.