Carcel

Most houses have a line going from the heater to the tap, not a loop, so the water just sits in the pipe waiting for pressure behind it to push it out of the tap. The cold water in the pipes can’t be recirculated. I suppose you could plumb a loop through the whole house and constantly rerun the cooling water through the heater but that kind of defeats the energy savings from a tankless heater. That loop becomes a really long skinny tank that’s right next to all of your taps.

The water in the pipes is still cold. Tankless heaters are endless, not instant. You still have to wait until the cold water is pushed out of the pipes, same as with a tank. Tankless heaters are still installed in the same central location as a tank and the hot water has to come from that point.

The law requires public domain for US Government works. https://en.m.wikipedia.org/wiki/Copyright_status_of_works_by_the_federal_government_of_the_United_States