After reading MarshalN's articles on the importance of water, I felt the urge to try something like that too. Of course, one does know that different waters give different brews, but how different exactly?
Experiment 1: Tap water vs. Evian water (I could not get any better), both boiled in an electric kettle. I used Purple Yi Wu 2010 as a test-tea as the tea is very sensitive to water used.
I took two bowls from the same serie, but about the same amount of tea to both, steeped the tea and waited. The difference was clear in less than a minute.
Tap water is on the left.
In detail, tap water
First, I observed the aroma. The difference was huge - the Evian smelled like nice, darker young Yiwu, sweet, full, with some fruit and nuts. The tap water smelled hollow, dry and not that good.
Looking at the bowls, one may immediately see that the tap water yields a lighter brew. What you may not see at the 0th sight, but it should be seen at the first sight, the Evian bowl is much more cloudy - it is not that I was out of focus. Peculiar, is it not?
The taste was very different too. Despite the poor aroma of the tap water bowl, both bowls tasted very nice, but very different.
The tap water bowl tastes good, full, fruity (it is that dark fruit style Yiwu). If I try, I guess I do taste a bit of chemical stuff in there (not chlorine, it is some other disinfection. It is not too bad though, I like how the bowl tastes.
The Evian bowl tastes also good, also full, but it is much more like the "honey and nuts" Yiwu style. It is much more nutty and much less fruity than the tap water.
So, although one would naturally expect some difference when using different water, the takehome message here is that the tea can be diametrally different even using "normal" waters. This was boiled in an electric kettle, none of the waters had significant flaws or superpowers.
Boiling tea is also an issue. It is well known that brewing water in a clay kettle on real fire is great. Tetsubin on a heating plate is also good. Some people boil water in a pot on a gas burner. How does it affect the water? Today, I pitted tap water boiled in an electric kettle (metal everywhere) against tap water boiled in a pot.
...There will be no photos as there was no significant difference in the color, aroma or taste.
The importance of material is vast though. Plastic kettles are, unles propertly cleaned, not much good in my opinion.