Water and coffee: It’s just water, right?


You’ve meticulously selected or roasted your coffee beans, ground them just right and brewed your coffee to perfection. Or have you? How much attention did you pay to the water you used? Your delicious brewed coffee is 98% water, so it might just pay to spend a little time understanding the effect water can have on your brew.

Water chemistry is complex. What we are particularly interested in is mineral levels of the water and how the minerals interact with one another. Even more importantly, how they interact with your coffee. Too many or too little of certain mineral content will detrimentally affect your extraction and could result in either a bland or over-extracted, harsh and bitter brew.

Hard and Soft Water

“Hard” and “soft” are terms used to describe water with high and low mineral content, respectively. The source of the water impacts the water “hardness”. Underground water is harder than surface water (eg. from rivers and streams). This is because underground water has far greater exposure to minerals over time. Magnesium, calcium and carbonate are important minerals to monitor.

In addition to minerals, water may contain pollutants, water treatments, or even the chemicals used to disinfect water mains pipes. The material used to construct the water pipes can also affect the chemical composition of the water, leaving chlorine and hypochlorite traces that will taint your coffee experience!

Water pH

The pH of water is affected by minerals and contaminate content. You guessed it! This is also important for your brew quality.

Ideal Water

The Specialty Coffee Association (SCA) has described the standards for high quality water. You can see these on the SCA website. In general, most water around the world is too high in both carbonate hardness and total hardness and need some treatment to elicit a perfect brew.

These basic filtration methods can improve your water:

  • Micron filters remove particles and bacteria

  • Carbon filters remove chemicals, pesticides, bad tastes and odours

  • Magnesium cartridges add magnesium (essential for extraction of desirable flavours)

One Final Piece of the Puzzle

Often overlooked, yet vastly important is carbon dioxide (CO2) in the beans themselves. Not technically part of the water problem, CO2 forms when the coffee is roasted and becomes trapped inside the bean. Coffee beans release the majority of CO2 in the first few days following roasting. This is a whole other blog post in itself – but simply put, the CO2 reacts with hot water to form carbonic acid, which alters the pH of the water and results in an acidic, sour and tangy brew.

What to do?!

In a commercial setup, water is tested, and the mineral content is analysed. Appropriate filtration or re-mineralising is undertaken to restore ideal mineral content. While this might be too much for the office, there are a few easy solutions for improving the water for your home or office brew.

Water Solutions

  • Water filtration jugs, such as those with Brita filters, remove chlorine and reduces carbonate hardness (acts as a water softener), and also help to reduce copper and lead particles.

  • Bottled water is generally well balanced and sits within acceptable limits of hardness and other chemical content

  • Third Wave Water has developed a sachet for optimal remineralisation of distilled water (which is completely devoid of any minerals)

  • If you are quite enthusiastic, you can make your own balanced water by finding a recipe using minerals available from the supermarket!

Coffee Bean Tips (to reduce CO2 related issues)

Filter Roasted Beans

  • Allow 3-4 days post roast to allow the bulk of CO2 to escape

  • If you need to use fresh beans, increase your bloom time to 45sec, blooming rapidly releases the trapped CO2

  • Tip out any run through from the bloom

Espresso roasted coffee

  • Allow 10-14 days post roast to allow CO2 to be released

  • Most espresso machines do not bloom reliably, so it is not recommended to use this method to force a rapid release of trapped CO2. You should allow the beans to mature naturally.

Getting water quality and CO2 content under control are very simple ways to take your brew to the next level – give it a shot!