水道水で年1回、井戸水なら年2回の水質検査をお勧めします。

tbd

We recommend that mains water have a water-quality test carried out once a year, well water twice a year.

今日は体調が悪い。あの井戸水が原因だ。

tbd

I feel out of sorts today. That well water is why.

I don't feel well today. That well water is the reason.