Ask any barista well versed in the art of brewing an espresso regarding the foremost ingredient responsible for ruining the taste of coffee and tea alike and I am pretty sure s/he will not hesitate to respond 'the water'. In fact, I believe the majority of Starbuck locations rely primarily on water filtration equipment for all their coffee and tea drinks given filtered water regardless of the source, i.e., city or well, enhances the taste of coffee/tea and not just drinking water alone. This in itself should tell you something regarding the importance of choosing the right water in brewing espresso. On another note, while purified water won't kill you, it remains the 2nd best choice compared to 100% natural Spring water given distilled and purified drinking water are stripped of minerals in the process. In contrast, natural spring water provides a wealth of minerals beneficial to the human body. Here we would venture an educated guess that it all comes down to cost in which event it has to be cheaper for a company like Starbucks to install its own water filtration system rather than purchase natural Spring water for making all its coffee and tea beverages. All considered, unless you own a coffee shop/cafe like Starbucks responsible for brewing hundreds of thousands of coffee/tea drinks on a daily basis with over 40,000 stores worldwide, given the price of a gallon of Spring water, we highly recommend using 100% natural Spring water for brewing your own espresso given it's not going to empty your wallet!