July 4, 2018

Testing Water in Pursuit of Excellent Coffee


As I watch the slow drip of my morning pour over, I like to tell myself that this coffee counts towards my daily intake of water. After all, every brew is up to 98% water.

But in turn, this means that the type of water we use has a dramatic impact on the flavour and quality of our coffee. If you really want the most delicious coffee possible, you have to use the right type.

I spoke to Ivan Mora, a barista at La Colectiva Café in Madrid, to learn more about this and how he’s using custom water blends to brew exceptional coffee. Here’s what I discovered.

Lee este artículo en español En Búsqueda de la Mejor Agua para Preparar un Café de Excelencia

Water can have significant impact on your coffee

Cold and hot brewed coffee. Credit: Matt Hoffman

What are TDS and PPM?

Water is very rarely just water. It will always have something called Total Dissolved Solids (TDS); these are miniscule minerals and organisms. Be they from the soil, the water treatment, or the water supply system, they will be present in the liquid and affect the final outcome of your brew.

However, the manner and extent to which they will affect your coffee depend on what the compounds are – and how many parts per million (PPM) there are of them in the water.

Magnesium, calcium, and bicarbonate are three common compounds, and they all have a strong impact on the flavor of your brew. For example, Maxwell Colonna-Dashwood and Christopher Hendon found that bicarbonate works as a buffer, regulating the acidity in your coffee. If you have the wrong amount, your coffee might taste dull and flat.

“It’s really hard to taste the difference in TDS levels when drinking the plain water,” Ivan says, but he argues that the real difference is noticeable once you start brewing coffee. The various minerals affect not just how the coffee tastes but also how it extracts.

You might also like How Grind Size Can Help You Brew Better-Tasting Coffee

“If you have irregular water, you will have an irregular brew,” Ivan stresses. “If you have acceptable water, you will get an acceptable brew. Ideal water will give you a superior brew.”

But what is the ideal type?

TDS meter in water

Measuring the TDS of water samples. Credit: Fernando Pocasangre

Testing Different Types of Water

Ivan has tested multiple types in the hunt for the best-possible filter brew. He tells me that he believes the ideal type has between 75 and 180 PPM mineral content. And in fact, he’s created a personal blend by combining various high-TDS and low-TDS bottled waters to create precisely 137 PPM.

He recently held a tasting session focusing on the differences in the taste and aroma of a coffee when brewed with tap, filtered, and his blend. The preparation for all three cups was identical; the only variable that changed was the water.

The result? “Tap water had a really unpleasant taste, I couldn’t tell you what the taste was exactly, but it was unpleasant,” he says. “Filtered gave the coffee a very acidic taste.”

However, when brewing coffee with his personal blend, Ivan describes the coffee as tasting “full bodied, clean and with no noticeable defects.”

As an additional experiment, he then brewed the coffee under the same conditions but using standard bottled water. However, high levels of bicarbonate in that particular brand killed the aromas and affected the taste of the brew.

In other words, water matters. But it isn’t always easy to select the best kind.

Pouring water on coffee grounds

Coffee extraction with tap water. Credit: Fernando Pocasangre

The “Perfect Water”: Does It Exist?

Let’s say that you want to improve your brewing through using great water but, unlike Ivan, don’t want to conduct lots of experiments. The good news is that the SCA has published their guidelines:

“Water for coffee extraction should: Be odor free and hygienic.
Have a total hardness of between 50–175 ppm CaCO
Have an alkilinity of between 40–75 ppm CaCO(2.2–4.2 °d)
Have a pH of between 6–8.”

But how easy it is to actually achieve this? Well, the quality of tap water varies regionally and on a daily basis. Bottled can create more consistency, but not all brands have the same composition.

And as Christopher Hendon says, while still advocating the use of a magnesium-rich type, “there is no one particular perfect composition of water that produces consistently flavoursome extractions from all roasted coffee.”

So, you probably won’t be able to get the “perfect” water every single time. But you can improve the quality by sticking to the SCA guidelines.

Freshly brewed coffee. Credit: Nathan Dumlao 

“Filter Water” vs “Espresso Water”: Is This a Thing?

Should we be using the same type for espresso as we do for filter? According to Barista Hustle, not always.

And filter coffee can give clarity to the different flavor and aroma notes in coffee –  notes that might not be as prominent in an espresso. This is especially true for a latte or cappuccino, say, where milk will further affect the taste.

Ivan tells me, “Due to the complexity and personal touch that goes into controlling every aspect of the brewing process, we use the blend for filter coffee to enhance these nuances.”

brewing coffee

Brewing AeroPress coffee with tap water. Credit: Fernando Pocasangre

Tips for Brewers

We’ve talked a lot about PPS, bicarbonate, and other standards, but what water should you actually be using?

Remember, all bottled brands have different mineral compositions, while tap water varies according to the region.

“Pay attention to the type of water you’re drinking and reach out to your water supplier to find out what’s in the water,” Ivan advises. “The main thing is to be informed about the water you’re using so you know what can be improved.”

And for those of us coffee-lovers who want a great cup without making our own personal blend? Check the label on your bottle and compare it to the SCA standards. Try a few different brands with the same coffee to see which you prefer. And then, you can also try seeing how different brands suit different coffees.


Brewing Chemex coffee. Credit: Fernando Pocasangre

When we brew coffee, we consider the origin, processing method, and roast level. We track the grind size and brew time. So why aren’t we paying more attention to water?

It has a significant impact on the flavor of your brew – and with a little experimentation, we can use this to unlock a coffee’s most complex, delicate notes.

Enjoyed this? Want to find out more? Check out What Café Owners & Baristas Need to Know About Water Quality

With thanks to Ivan Mora and Tim Sturk for their insights.

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