Water for coffee

Water for brewing has become a hot topic in recent years - and the conversation keeps growing.

Tap water is rarely the optimal choice for unlocking a coffee's full potential. The best strategy when choosing water is simple: find out what your roaster recommends. In Copenhagen, coffee is often brewed on soft water after reverse osmosis filtration. In Munich, you'll more commonly find a filter that brings mineralisation down from 260–280 ppm to somewhere around 90–150 ppm.

We use ppm to measure Total Dissolved Solids (TDS) - as our reference scale, since it's the most widely adopted in the coffee world. The German hardness system works quite differently, and mg/l also comes up frequently, though it's nearly identical to ppm in practice. Measuring is straightforward and affordable - we use a device from Xiaomi.

The easiest way to start experimenting is to pick up a few different bottled waters with lower mineralisation — under 150 ppm. Brew two cups with the same beans and the same recipe, changing only the water.

Total mineral content, however, tells you nothing about composition. How much magnesium is in your water — how much calcium? Is this still a coffee water post or a chemistry* lecture, you might ask? Fortunately, it's simpler than that - and you can have fun with it.

Companies like Third Wave Water offer ready-made mineral mixes - just add to distilled water. Apax Lab takes it further: alongside their premixes, they give you the opportunity to build your own recipe. My own journey with Apax Lab started at a Brewers Cup competition, and I'm glad it became part of my daily ritual.

The best solution for you might not be as complicated as it seems - but finding it is a journey worth enjoying. Cheers!

*If you're genuinely curious about the science, there's plenty out there to explore. Water for Coffee book is where I'd start.