noun
water purifier
A device that purifies water, typically for drinking. Often used in household or commercial contexts.
新しい整水器をキッチンに設置した。
I installed a new water purifier in the kitchen.
Compound of 整 (sei, 'adjust, arrange') + 水 (sui, 'water') + 器 (ki, 'device'). The exact origin is uncertain, but it likely refers to a device that treats or conditions water.