Ingredients 101: Water
There are a lot of opinions on this, but my recommendation is to start by using whatever type of water you like to drink.
This is what I personally prefer to drink. I’ve also found that it’s the most cost-effective method that yields the “cleanest” tasting brew. I have a counter-top filter that I just fill with tap water. So I have clean, filtered water handy whenever I want. I'm a big fan of the Berkey Water Filtration system (full disclosure, I'm an affiliate of theirs but I purchased my system with my own money and only became an affiliate after I had such a great experience with the water! It's truly the best-tasting water I've ever had, and it doesn't strip beneficial minerals out of the water which is great for fermentation.)
Lots of bottled water is labeled “spring water” when it’s really just repackaged city water. But real spring water is a really good option for kombucha. The minerals in the water are good for your kombucha. The downside is that you’d be purchasing bottles of it, which isn’t always the most cost-effective or environmentally-friendly. But if you have it around, you can certainly use it in your brew!
A lot of people have success with using tap water, but it depends on where you live. I live in Los Angeles, and batches that I’ve brewed with tap water always seem to have a sort of dirty or musty taste to it. But you can always experiment and try it out (just make sure you have backup SCOBYs and starter tea on hand!).
Most tap water contains chlorine, so make sure you boil your water for 15 minutes prior to using or let it sit in an open container for 24 hours to let the chlorine evaporate out of it. You don’t want chlorine killing the good bacteria in your brew!
I don’t recommend using it because it’s essentially “dead water” that’s had all its minerals stripped out of it. Those minerals actually help with the fermentation process, so it’s not necessary at all (and may even be harmful to your brew in worst-case scenarios) if you use distilled water.
*Pro tip: Whatever kind of water you end up using — if you have the space for it and if you like to have big brewing days where you brew multiple gallons of kombucha like I do, it’s handy to have a few spare gallon jugs you can keep refilling with filtered water. That way, you’ll always have plenty of water on hand to brew whenever you want!