I wonder if the OP believes 15 min. of boiling will increase the temp of the water. S/he said "hot pot or kettle". If a kettle will do, he's probably not cooking anything inside it, which would make a 15 minute boil simply wasteful. I've not heard the term "high boil". What temp is that? Boiling is 212 degrees, and the only way to exceed that is to pressurize it.

Is she steaming a face, perhaps?

If it's to purify contaminated water, is 15 min. necessary? For purification purposes, a pressure cooker would be better because some things can survive in the 212-240 degree range.