June 21, 2018

What Café Owners & Baristas Need to Know About Water Quality


Great coffee beans: check. Great equipment: check. Great recipe: check. So why doesn’t your brewed coffee taste great?

It could be the water.

Water makes up as much as 98% of your coffee, meaning that poor-quality water can turn your beverage into a flat, bitter, or vinegary experience. And not only can it obstruct extraction or produce unpleasant flavours, but it can also cause significant equipment problems.

To find out more, I spoke to Paul Stack, Operations Director at Marco Beverage Systems, which creates award-winning hot water dispensers and brewers, including the Marco MIX (which has an inbuilt filter) and SP9. I also reached out to two of Marco’s customers: Nathan Retzer, owner of Quarter Horse Coffee in the UK, and Taylor Cowan, Co-Founder of Spirit Tea in the US.

Let’s see what they had to say.

Lee este artículo en español Lo que Necesitas Saber sobre la Calidad del Agua


Using a Kalita Wave and Marco SP9 to brew coffee. Credit: Five Senses Coffee

The Taste of Water

We think of a “watery taste” as simply referring to strength and body, but actually, water often comes with its own set of flavours.

Water might contain minerals, dissolved substances, and even additives, all of which can have an impact on your coffee’s flavour. Drinkable water is not always delicious water.

And as Nathan tells me, “Coffee is mainly water, so any flavour the water comes with will taint the coffee.”

You’ll find minerals such as calcium, chlorine, fluoride, and iron. Nathan says, “You can taste minerals, so the more of them, the more you can taste them with the flavour of the coffee.”

Of course, not all minerals are bad – in fact, some of them can even help with extraction.

control brew time

Tea and timer: it’s easy for customers to control brew time, but good extraction still relies on water quality. Credit: Spirit Tea

When Water Causes Extraction Problems

Brewing coffee is all about extraction: getting those flavour and aroma compounds out of the ground coffee and into the hot (or cold!) brew.

And having the right amount of minerals like magnesium and calcium can actually help baristas to achieve a better extraction. Magnesium aids in the extraction of fruitier and sharper flavours, while calcium enhances creamy notes.

This is due to the positive charge of their ions. Generally, flavour compounds in coffee are negatively charged, so they become naturally attracted to the positive charges of minerals such as magnesium and calcium.

But if there are too many of these minerals, that isn’t so good for extraction either. They can crowd up the water so that there’s less room for flavour compounds.

You need the Goldilocks of water: not too hard, not too soft, just right.


Freshly made Chemex coffee: this black brew is still mostly water. Credit: Sebastian Chodzinski

Is Your Water Damaging Your Equipment?

But it’s not just the coffee that’s affected by the water – your equipment is too. “You need to be mindful of the quality of the water you are putting into your machine,” Taylor explains. “If you are using tap water or you are using a bad filtration system, that is going to destroy your equipment, in addition to making your beverages taste bad.”

Mineral-rich water, also known as hard water, can cause particular problems. As hot water evaporates, minerals can be left behind in your equipment. These deposits, which are also called limescale, can then harm its performance.

Deposit build-ups can form on your boiler’s heating element, for example, which will then make it harder for it to efficiently heat up water. Limescale (which is primarily calcium) can also clog up pipes, preventing the correct flow of water and steam.

The end result: increased maintenance and cleaning, reduced efficiency and consistency, and potentially even damaged equipment.

Nathan recommends periodically changing your filter to protect against this. “Water filtration is very affordable and can save you thousands in the long run,” he stresses. “Why spend 8–12,000 on a nice espresso machine if you have it seize up in two to three years?”

The Marco MIX, which has an inbuilt filtration system. Credit: Marco Beverage Systems

How to Measure Your Water Quality

At the very least, café owners and baristas should know the following information:

  • Total Dissolved Solids (TDS)

TDS measures any minerals, salts, metals, or other solids that have been dissolved in the water. As Paul explains, “Minerality concentration in water is a significant taste impactor, which can be negative and positive depending on minerals and concentration and can significantly affect extraction.”

The SCA recommends a TDS of “between 75–250 mg/L TDS, with a target of 150”.

  • Water Hardness

Water hardness refers to the concentration of specific minerals in the water: calcium, magnesium, iron, and manganese, along with some others in smaller amounts. In other words, water hardness forms part of TDS.

The more of these minerals in the water, the harder it is. The less, the softer it is. And remember, water that is too hard or too soft will lead to extraction problems. The SCA recommends “1–5 grains per gallon (gpg) or 17–85 mg/L, with a target of 3–4 gpg or 51–68 mg/L.”

Paul emphasises that calcium is the primary component of limescale, something which means that water hardness is key to equipment longevity.

  • pH levels

pH levels also play a crucial role. A quick science class recap here: water is neutral if it has a pH of 7.0, alkaline if it is more than that, and acidic if it is lower than that.

The more neutral the water, the better. The SCA recommends using water with a pH of 6.5 to 7.5. Highly alkaline water can often result in a flat cup and end up contributing to limescale.

cup of coffee

Freshly brewed, ready to drink. 

Don’t let poor water get in the way of great coffee. If there’s one thing that all of us in specialty coffee can agree on, it’s that every detail counts. And good-quality water can protect your coffee quality and your equipment longevity.

Please note: This article has been sponsored by Marco Beverage Systems.  

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