I did something very similar to this in 2015. I bought an adaptor and a commercial grade hose, attached the hose to an indoor shower, turned it up as hot as I could get it, and snaked it outside to where I was able to climb a ladder to the roof. The first thing I did was clear the downspout so the water had somewhere to go, then I sprayed the hot water on the ice, top, bottom, and sides, in 3-4 foot sections. After that, I could pull them out easily and toss them to the ground. It took me less than 30 minutes to clear 20 feet of gutter of some of the most horrific ice dams you could imagine.
