Arrowhead Mountain Spring Water - I Have My Suspicions
Early on in my bread baking - at least this latest go-round - I noticed that my reverse osmosis water was not working very well in my yeast breads. I read my recipes a little more closely and saw that they recommended spring water. So I went out and bought Arrowhead Mountain Spring Water and found a big improvement.
(For those not in the know, the reverse osmosis process removes everything from the water except the water itself; so you end up with theoretically pure water.)