I do not know if this topic was discussed. A search for tea and water yields too much to go thru.
What is the best water for tea and how much does the water influence the resulting taste of the brewed tea?
For most of my teas I use our tap water which is loaded with lime. For fine green and green oolongs I use bottle water since I then use my glass tea pot in order that I can "see" the temperature and the bottle water will not mess-up the pot with lime deposits. I could never find a difference in taste between the 2 waters. Sometimes for the last 2 infusion I use the tap water if the tea gave more than the usual and again there is no difference.
I have tried rain water and that made the tea taste flat. May be not enough oxygen and no minertals in it.
In Tokyo there is a railroad station called O-Cha-ni-Mizu, Teawater. May be there was once a spring giving better water for tea