Wouldn't that ice up?

Sounds like a dumb idea once it’s cold enough to ice up

in many former soviet bloc countries they have systems that send out the steam from the power plants turbine systems into vast networks of underground pipes that run the steam-powered radiators in the massive commieblock suburbs, also heating the water for baths (and in soviet days baths were fairly common and readily available, imagine compared to the austerity of now how in some ways it was way better for them)

the incredible waste of heat energy that is happening with most power plants is quite mind blowing, in my opinion

but this thing the japanese are doing is cool, they have thermal springs everywhere, that's why the place is constantly rumbling with all that magma moving around

bulgaria also has a massive wealth of thermal springs and much of russia and poland and western china also have massive amounts of hot underground water... it's a resource and literally a very large amount of energy available if you use it

Unless they have a very abundant and cheap source of water and energy., it doesn't seem cost effective. The rest of the world spreads salt to lower water freezing point.