残のこし湯ゆ

noun, noun or participle which takes 'suru'

leaving bathwater for later use (e.g., laundry)

Refers to the practice of not draining the bathtub after bathing, so the water can be reused for washing clothes or other purposes. Often used in contexts of water conservation.

• 残のこし湯ゆで洗せん濯たくすると水すい道どう代だいが節せつ約やくできる。

  You can save on water bills by doing laundry with leftover bathwater.

• 母はははいつも残のこし湯ゆを洗せん濯たくに使つかっている。

  My mother always uses the leftover bathwater for laundry.