Washing with water only (without using soap or detergent); rinsing by water.
食器はまず水洗いしてから、油汚れがひどいものだけ台所洗剤で洗う。
I first rinse the dishes with water, then wash only those with heavy grease using dish detergent.
赤ちゃんの服はすぐに水洗いしてから洗濯機に入れたほうがいい。
It's better to rinse the baby's clothes with water immediately before putting them in the washing machine.
この汚れは水洗いだけでは落ちないので、少し洗剤を使おう。
This stain won't come out with water alone, so let's use a little detergent.