The Water Effect: How Water Affects Your Coffee

One might wonder why is it that coffee produced by a barista at a cafe often tastes different than brewed at home with the same coffee. Or why the same is observed when you brew the same coffee as your friend whom you split the same bag of coffee with.

Given that everything is identical, water might just be the culprit.

Your coffee brew is made up of mostly water - about 90% in espresso, and 98% in filter coffee. This is why many brewing guides recommend using clean, odourless water, free from impurities.

Water also acts as a solvent during the brewing process. Its mineral composition can affect the extraction of different flavour compounds from the ground coffee beans into your cup. This means that different water can extract coffees differently, even when brewed with the same equipment and brew recipe.

Why do these variables matter?

To better understand the difference, we’re using the Water Brewing Standards from the Specialty Coffee Association (SCA) as a reference. The specifications below don’t suggest that this is the perfect water for all coffees, but it certainly is a good starting point. 

Water for Brewing Standards / sca.coffee

Odour and Impurities

Clean, fresh and odourless - these are the minimum requirements for the water you’re using for brewing. Off-flavour from impurities might show up in the coffee you brew.

A common substance present in tap water is Chlorine, which is used by water treatment facilities to kill bacteria and microbes. Chlorine has an oxidising effect that makes coffee more bitter, and in the case of espresso, ruins crema formation. An easy way to remove these impurities is through an Activated Carbon filter, three-stage domestic water filtration systems, or water filtration pitchers like the Brita.

Hardness

With Hardness, we begin to touch on the brewing efficiency of water. Also known as General Hardness or Total Hardness, it refers to the presence of Calcium and Magnesium in the water, along with other ions. With an adequate concentration of these minerals, water becomes more effective at extracting compounds such as 2-Methyl Pyrazine (which is responsible for nutty and chocolatey flavours), and Furnaeol (which gives coffee fruity and berry-like flavours).

This is the reason that distilled water is not recommended - no minerals means less-efficient flavour extraction. However, more does not mean better as Calcium and Magnesium are responsible for limescale build-up and corrosion in metal parts of brewers such as coffee machine boilers and pouring kettles.

The SCA recommends a Hardness range of 50-175ppm, though some other resources cite 80ppm as an optimum balance of flavour and machine protection.

Author’s note: There are many units used for hardness, but for simplicity, we will stick to ppm or parts per million for this article.

Alkalinity and PH

Another aspect of water is called Alkalinity, also known as Carbonate Hardness.

This refers to the buffering capacity of water, or the ability of water to resist changes in pH. pH (or Potential Hydrogen) is a scale used to denote the acidity or alkalinity of liquids. Coffee, being a weak acid, depends on a suitable amount of Alkalinity in the water to promote good extraction.

Excessive Alkalinity will make the water very resistant to changes in pH, so a naturally bright coffee will probably taste bland when brewed. Low Alkalinity will cause acids to prevail in the brew, which may cause a sweet, balanced coffee to taste weak and sour. The SCA recommends a balanced Alkalinity of 40-70ppm.

Measuring Water

Given that we have an idea of what numbers to look out for, how do we measure the water we have at home? The simplest, but also most accurate way is through measurement of Total Dissolved Solids (TDS). A cheap TDS meter can be had for about $10, and it’s as easy as sticking the probes into the water to test.

If you are using the Morning Machine, it comes with a built-in TDS reader and will be able to show you the status of the water you put in it. You may access it via settings (holding the return and confirm buttons), scrolling through to “Machine Info” and finally to “Water Status”.

The constraint with measuring TDS is it gives a readout that includes all residue in the water, including inorganic salts and organic matter. It might be a good indicator of how hard or how soft your water is but tells you nothing about the concentration of General Hardness and Alkalinity.

A relatively more accurate method would be to get test kits that measure GH (General Hardness) and KH (Carbonate Hardness). These require more effort to use, but they give you a better idea of the brewing efficiency of your water.

The most accurate way would be to contact your water treatment plant or supplier for exact specifications of the water you have access to.

Better Water at Home

If the water in your area is a far cry from the SCA Standards or even your neighbourhood cafe’s water specifications, here are a few things you can do:

    1. Buy bottled water. There are a few brands that come close to the SCA standard. Check your grocery for available bottled water options, which usually list the mineral concentrations on the label. Of course, a big downside to bottled water is the negative environmental impact, a better alternative would be to… 

    2. Make your own water. All it takes is distilled water and mineral salts. You can look for the minerals yourself (don’t forget the bicarbonates for Alkalinity!), or use branded mixes such as Aquacode and Third Wave Water.

    3. Use a Specialised Filtration Solution. These range from the easy-to-use Peak Water pitcher, to a Reverse Osmosis System with a remineralisation cartridge. This means you can use what water you have, and treat it yourself at home before brewing.

    4. BONUS TIP: If you’re a Morning Machine user, we have a water filter attachment coming your way to help filter out impurities and produce softer water for your brew. Stay tuned for the drop!
These are just fundamentals on understanding water and how it affects coffee. If you’d like to learn more, our recommendation on reading materials includes the publication - Water for Coffee by Maxwell Colonna-Dashwood and Chris Hendon. For crafting your own custom brew water, Coffee Ad Astra is an excellent resource as well.

Now, go off to try making your own brew with water that matches the TDS standards we spoke about.

Words by Jon Choi @theheadbean

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