Here are some pictures of a spring in Aso, Japan, only a few miles from the tea estate of the Nagata Family, our growers. The sign in the picture reads "Teno no Meisui" (手野の名水), or "Famous Water of Teno." (Teno is the name of a district of Aso.)
It doesn't look like much, but the spring water that issues out of the crack in the mountain there is truly delicious. And it's free. Of course, commercial operations aren't allowed to hook up a siphon, but individuals can come with their own containers and take some of this delicious water home.
The water here tastes better than any water I've ever had. Some of the bottled water available nowadays isn't bad, either, and green tea brewed with this kind of water will taste so much better than if it's brewed with water right out of the tap.
If you've been brewing your Mellow Monk green tea with tap water, try this test: Brew your tea with bottled water (or even filtered tap water) for, say, one week. Then, try a cup or pot of tea brewed with tap water again. I think you'll taste and smell the difference.
After all, water is the life blood of green tea!