noun
purified water
Refers to water that has been processed to remove impurities, often used in medical, cosmetic, or laboratory contexts.
コンタクトレンズの保存には精製水を使います。
I use purified water for storing contact lenses.
Tap water, which is treated but not necessarily purified to the same standard.
Compound of 精製 (seisei, 'refining, purification') and 水 (sui, 'water').