I recently got interested in this...
I think this pH thingy is a thing for green tea..because I heard once the water is boiled, it turns automatically alkaline
I didn't notice it much, but I've found the water do play an important role when brewing green (the tea I drink most recently).
Here in China, I drink mostly Nongfu spring. It's the water from Zhejiang's Qiandaohu lake..a huge beautiful lake..the pH is around 7.0~7.2
Kangshifu bottle is somewhat cheaper...it's made from filtered tap water then the minerals are added. The pH is the lowest in China..is less than 6. It brews Puerh very well nonetheless.
Evian is super expensive in China...pH is around 7.1
My favorite is Kunlunshan..kinda expensive. It's from snow mountain of Tibet and Xinjiang area. The pH is 7.1 I heard.
Then there's Korean Samdasoo..volcanic water from Mt.Hala...pH is around 7.7...currently my favorite for Yancha.
dunno much about western brands