Depending on where you live and what comes out of your tap, you may need to improve the water you feed into your coffee machine, kettle, or French press. Water quality has a significant impact on the final cup, both by warding off off-flavors and by supplying the right mineral composition to interact with the coffee’s aromatic and flavor compounds.
When I previously spoke with Jose Lepe, director of sourcing and quality control for Sightglass Coffee, about whether filtered water is necessary for brewing, he emphasized that “water hardness is part of what is going to make your coffee taste right, so you need some of that minerality in coffee to help pull out the actual flavors.”
High-end coffee shops typically employ a water system built on reverse osmosis, which distills local water down to its purest H2O form and then remineralizes it to achieve the ideal balance. Not every major coffee city operates a system like this, but in places like Los Angeles, which according to Lepe has notoriously poor water for coffee, this approach is definitely in play.
The good news is that you can recreate this process at home without investing in five-figure specialized equipment.
Why consider making water for coffee?
There are several compelling reasons to explore custom coffee water recipes. Take the mineral composition of New York City tap water, often celebrated as the liquid gold standard. NYC’s water is soft, with low concentrations of dissolved minerals such as calcium and magnesium and only trace amounts of sodium, according to NYC.gov.
I spend much of the year in London, where the tap water tastes fine on its own, but the mineral composition can quickly choke the life out of any coffee machine with narrow water conduits if it isn’t treated with a descaler. (I know this firsthand. RIP steam wand.) London’s water carries roughly eight to 10 times the calcium content of New York’s. Las Vegas, Indianapolis, and San Antonio are just a few U.S. cities where the water is nearly as hard as London’s and considered extremely hard by standards.
Water hardness can be somewhat addressed with filtered water, but filtering removes most minerals without replacing any. It’s not as detrimental as pure distilled water (more on that below), but you won’t get the most out of your coffee experience. The real motivation for trying a “water recipe” is to protect your equipment while pursuing the best possible cup. We’re fully on board with that kind of dedication.
What is remineralized water?
Rather than relying on filtered water alone, remineralized water is simply distilled or reverse osmosis water that has specific minerals added back in — namely sodium bicarbonate and magnesium sulfate — in a precise ratio. Distilled water is easy to find at any grocery store or pharmacy, and so are the two minerals: sodium bicarbonate is commonly known as baking soda, and magnesium sulfate is sold as Epsom salt.
We’ll get into the specific ratios later, but if you’d rather not turn your kitchen into a makeshift chemistry lab, brands like Third Wave Water and Lotus offer simple mineral packets designed to add to distilled or reverse-osmosis-filtered water.
An actual recipe for coffee water
A common DIY water recipe uncovered on Reddit calls for adding 0.25 grams of baking soda and 0.76 grams of Epsom salt to one gallon of distilled water. This is the ratio the Specialty Coffee Association recommends. You’ll notice this recipe requires a kitchen scale that measures to the hundredth of a gram, unless you’re prepared to scale up to 10 gallons at a time.
Without that particular piece of equipment, another potentially simpler method sidesteps the scale entirely. It involves using standard measuring spoons to prepare liter-sized batches of mineral concentrates — one with Epsom salt and one with baking soda — and then adding easily measured portions of these liquid concentrates to a larger quantity of distilled water. (If that sends you scurrying back several paragraphs to investigate those ready-to-use packets, I completely understand.)
The perfect coffee water taste test
To assess the actual flavor difference with remineralized water, I brewed three cups of coffee in succession, using precise ground and water measurements with an AeroPress: one with pure distilled water, one with regular tap water, and one with remineralized water. I tasted each black once, immediately after brewing, then several more times as it cooled. I eventually added a splash of milk to each, since that’s how I normally drink coffee.
First things first: coffee made with pure distilled water was truly terrible. I had been forewarned and was prepared, but I was honestly shocked at how bad it was — somehow both hollow in body and carrying a pronounced tang that fell somewhere between acidic and metallic. Not recommended.
The tap water cup, which I already knew I enjoyed, soared by comparison next to the distilled water version, though it was also noticeably heavier in body.
After mixing the remineralized water with microdoses of both baking soda and Epsom salt for the amount of distilled water I was using, I was skeptical that such small amounts could make a meaningful difference. But I have to admit, they really did. The resulting cup displayed what can reasonably be described as balance: good body, strength, and brightness, without the odd tang of the distilled water version or the heaviness of the tap water.
Does this mean I would go through the trouble regularly? To protect my electric coffee makers and enjoy each cup a little more? You know what — I might just.