The water you use to brew your daily cup of coffee has an impact on how the coffee brews, the flavour you will experience and the overall character of the cup. If you are an espresso drinker, water will constitute around 90% of the coffee you drink, and if you prefer brewed coffee, you’ll be drinking over 98% water. In the last article I shared how water had influenced our coffee roasting, and this time we’ll take a look at some solutions to the ‘problem’. To begin we need to understand a little bit more about what it is in water that makes all the difference.

The following all comes from a non-scientific mind! It is fair to say I never really gelled with the sciences when I was at school, so understanding water has been a bit of a personal challenge. All too often I have been reminded of my days as a bewildered schoolboy, sitting in the Chemistry lab wondering what it was all about!

There are only two things I worry about when considering whether a particular water will be any good for brewing coffee: the mineral content, specifically calcium and magnesium, and the alkalinity.

Calcium and magnesium are flavour-carrying minerals, which makes them critically important if you really want to taste those flavour notes on the coffee bag. Too little of these minerals and a coffee can taste empty, while too many can cause the coffee to taste heavy.

Alkalinity is possibly even more important. This is the buffering capacity of the water. There are many acids in coffee and during the brewing process, the alkalinity in the water helps manage these acids. If alkalinity is low, the resulting coffee can be sour and sharp. Similarly, if there is too much alkalinity, your coffee can taste flat.

Combining the two we can arrive at an ideal brew zone which is represented by the complex chart below! The x-axis refers to alkalinity and the y-axis to the magnesium/calcium concentration. I am probably not the best person to talk through the various numbers on this chart, but I use it simply to represent the fact that there is an ideal brew zone.

So if you have spent all that money on a beautiful piece of coffee-making kit, have watched all the brewing videos own an expensive set of digital scales, then you probably need to spend some time learning a little about the water you use to brew that coffee!

Knowing Your Water Quality

It is actually quite important to know the quality of the water you currently have, particularly if you want to explore any of the options below. Knowing whether you have soft, balanced or hard water, helps you decide which solutions to choose. Fortunately, water companies have to analyse your tap waste and publish the results, which is a really useful tool! Head over to the website of the company that supplies your water and you should be able to find a water quality option, where you simply enter your postcode. Here are the results I get:

You can only use this as a guide, as it is the actual mineral content we are interested in. However, it is a good starting point and will prevent you from picking the wrong ‘solution’ below. In essence, the solutions are relatively simple, in practice, they are a little more complex! If you have hard water you want to remove minerals to bring your water down into the acceptable brew zone. If you have soft water, you need to add minerals. In my experience dealing with soft water is more complex than dealing with hard water. Some solutions work for both waters, some are more specific; some solutions are straightforward, some require commitment. The more precise you want to be, the harder you will need to work!

Do nothing!

  • Works for both hard and soft water
  • Geek level 0

If you are happy with how your coffee tastes, and are content with your daily brew, then doing nothing is perfectly acceptable. Sometimes we can overcomplicate life! Just be aware that hard water can cause scale in your beloved machine.

Use bottled water

  • Works for both hard and soft water
  • Geek level 1

I am not suggesting you start using bottled water to brew your coffee given the negative impact of single-use plastics. I am however suggesting you use bottled water to decide whether it is worth the trouble. If you want to know whether your coffee will taste better on different water, buy a bottle of Volvic (as it has the best mineral balance) and see what happens. You can then decide whether to choose one of the options below:

Brita style filters

  • Works for hard water
  • Geek level 1

Brita-style water filters are a great way to reduce the hardness in water, are relatively cheap and are simple to use. Unless you test the water afterwards you can never be really sure if you have produced acceptable water, but it is likely to be better than the hard water you currently have.

Magnesium Remineralising Filters

  • Works for hard water
  • Geek level 2

These work in the same way as the Brita filters but have an added chamber that remineralises the filtered water as it passes through. Again you can never be sure of the results without testing but these filters at least add something back, albeit in small amounts.

Peak Water

  • Works for hard water
  • Geek level 3

This filter broadly works on the same principle as the Brita style filters but has the addition of a variable bypass. Essentially the filter removes minerals from hard water but to rebalance it you allow some unfiltered water to mix back in. The amount of unfiltered water you use depends on the hardness of your water. As a nice touch, the Peak comes with water testing strips, so you can measure your tap water and the water you produce.

Third Wave Water

  • Works for hard and soft water, in conjunction with a Zero Water filter
  • Geek level 4

Third Wave Water are sachets of minerals each of which can remineralise 2 litres of distilled water. To me using distilled water is no better than using bottled water, so instead, I use a Zero Water Filter. Unlike the filters above, the zero filters are designed to remove everything from your water, effectively giving you a zero base to work with. You can then add a sachet of Third Wave Water to create the perfect brewing water, with no testing required. Incidentally, there is a sachet for brewed coffee and a different combination for espresso.

DIY Water

  • Works for hard water with a Zero Water Filter
  • Works for soft water
  • Geek level 5

It is possible to remineralise water using two common products – Epsom salts (magnesium sulphate) and sodium bicarbonate (baking soda). This is the method we use at our Roastery, where we remineralise 25-litre barrels. There are two approaches: remineralise existing water (which requires testing) or filter the existing water and remineralise, which doesn’t need testing.

We tend to only use magnesium when we remineralise water as calcium has a tendency to cause scale. I also suggest a little bit of caution when remineralising for espresso machines. Any mineral content can cause scale to a certain degree so I would urge less is more in this instance.

The method is straightforward and best explained in Matt Perger’s blog, Barista Hustle. I use this approach at home alongside the Zero Water filter.

Like everything with coffee, the more you put in, the more you get out. There are some simple ways of remineralising water, and then there are more complex. The actual amount of minerals used in each case is very small, and this can make it challenging as a small error can quickly take you out of the ideal brew zone. Personally, I have been remineralising water for years and have come to the conclusion that it really does work and my coffee tastes much better for it.

Gareth Kimble is the founder and co owner of Carvetii Coffee

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