noun
adding hot water; topping up with hot water
Refers to the act of adding hot water to a bath or pot to adjust temperature or volume. Often used in contexts like bathhouses, cooking, or tea preparation.
お風呂がぬるくなったので、差し湯をした。
The bath got lukewarm, so I added hot water.
差し湯をしながら、ちょうどいい温度に調整する。
Adjust the temperature to just right by adding hot water.