节约用水的英文表达是 "conserve water"。这个说法来源于英文动词 "conserve"，意为"保存，节约"，加上名词 "water"，即 "水"。

一些英文例句如下：

We should all do our part to conserve water.

By taking shorter showers and fixing leaks, we can conserve water and save money on our water bills.

Planting drought-resistant plants and using mulch in our gardens can also help us conserve water.