ichidan verb, transitive verb
heat up; bring to a boil
Transitive verb meaning to heat a liquid until it boils, or to bring something to a boil. Often used with water, soup, or bathwater.
お湯を沸き上げてから、パスタを入れます。
After bringing the water to a boil, I add the pasta.
風呂を沸き上げるのに
It takes time to heat up the bath.