Inspired by this video from James Hoffman:

I wanted to optimize water for brewing my coffee.

However, as Hoffman notes, buying bottles of water optimized for coffee leads to plastic waste. Since I actively try to reduce waste (e.g. buying used from eBay), I researched a “practical water setup” minimizing plastic waste: purifying water with a special filter jug, then remineralizing that purified water with a precise recipe. I bought the special filter jug used from eBay.