Water is to coffee what a pen is to paper. They go hand-in-hand; one is pointless without the other (yes, water is pointless without coffee).
But just like those people who like to write on thick parchment with a nicely inked pen, a good coffee should be enjoyed with the best water available.
Here’s why you should use high-quality water to brew your coffee.
Hard and soft water
98 percent of a cup of coffee is made up of water. The quality of the water, then, has a significant role to play in adjusting the taste of a cup.
Hard water (that is, water filled with minerals like magnesium) and soft water (often more ‘pure’ distilled water) varies from place to place in the United States. In the below map, dark purple represents the distribution of soft water, while red represents hard water across the country. White space is somewhere in between:
Sure, it might be reasonable to assume soft water, given how glacially ‘pure’ it is, is the best water to use in a cup of coffee. But, according to MIT chemist, Christopher H. Hendon, you’d be wrong.
You see, hard water is rich in magnesium, calcium and bicarbonate ions. These compounds are ‘sticky’, and they grab onto certain compounds found in coffee when an attempt to make a brew is made. Because of this ‘stickiness’, hard water has more influence over the taste of your coffee. Magnesium, for example, is a particularly sticky compound, so hard water with lots of magnesium present will make your coffee stronger both in flavour and caffeine content.
But hard water can also have higher levels of bicarbonate, which Hendon says could lead to more bitter tastes.
Hard water is a gamble
Choosing hard water to brew with, then, is a gamble. The risk of diminishing good beans is quite high, but so is the reward of adding complexity to your cup of coffee.
Soft water, however, contains sodium, but it lacks sticky compounds that can add character to a cup of coffee. This means that you’ll likely get a much stronger tasting cup of coffee if you use hard water instead of soft water.
Water pH: Is it a factor?
Water can have a high acid or alkali percentage. (Just FYI… ‘neutral’ water has a pH of 7). When it comes to brewing coffee, the bicarbonates in water work to regulate the acidity, and for a ‘stable’ cup of coffee, you’ll want some alkalinity to be present in your water, too.
But too much alkalinity will destroy that pleasant acidity that comes with a cup of coffee, and too low an alkalinity level will result in vinegary sour flavours. As put by Barista Institute:
- Acidic water is bad for extraction, but great for coffee flavour. (It will also result in faster corrosion of equipment).
- Your average tap water is good for extraction but bad for flavour.
Standards for high quality water
Most drinking tap water across the globe is hard water. If you live in a city especially, it’ll be hard water. If you live in London or New York, expect the hardest of the hardest (think about how many dirty pipes that stuff has to flow through…).
The Specialty Coffee Association (SCA) explain that the standards for minerals in water to produce a ‘stable’ cup of coffee are:
- Total hardness of 50-175 ppm CaCO3 (2,9-9,8 dH°).
- Carbonate hardness of 40-75 ppm CaCO3 (2,2-4,2 dH°).
- pH of 6-8.
However, it’s important to note that to achieve the ultimate balanced cup of coffee, you need to understand your local water makeup and adjust your brew technique accordingly. That, my friends, requires a coffee nerd.
Want our advice?
If you’re buying locally roasted beans, you can probably rest assured that they tested flavours using water with a similar composition to yours. That means that, to achieve a balanced cup of coffee (like your roasters would have before they put their beans on sale), you shouldn’t have to factor in water all that much.
You can also look up the hardness of your water online (and for those of you who are New Yorkers, call 311). By understanding your water’s composition, you can begin to produce the most balanced cup of your life (assuming that your water is hard).
After all, no risk, no reward.