water for coffee

Water For Coffee - Why Is Filtered Water the Best ?

Filtered water - it seems like a luxury, but when it comes to making great tasting coffee, we think it's an absolute essential...

Why's that? Well, in this post we'll explain everything, including the pros and cons of using different types of water for coffee.

Why is Water for Coffee important?

Water is the unsung hero of the coffee world. Don't believe us? Well, think about the composition of your morning coffee.

Water makes up 98% of it! Even in a tiny espresso coffee, the actual coffee is only about 10% maximum.

Furthermore, water acts as a solvent for coffee. This is because, on a molecular level, water has a polar arrangement - two hydrogen atoms with their positive electrical charge on one side, and one oxygen atom with its negative charge on the other.

This makes it super attractive to a wide variety of molecules. It’s so attractive in fact, it will pull apart the bonds of other molecules, causing them to dissolve into the water.

If you heat the water, all of its molecules will begin to move around quickly, making it an even more efficient solvent.

The flavour compounds of the coffee are brought out by the water. Finally, the water that you use has a huge impact on your brewing equipment.

We've discussed this briefly before, but hard water is not good for the longevity of any coffee maker.

The minerals tend to build up in coffee makers, leaving a chalky white residue that can impact the taste of your coffee and block holes in your appliances.

You'll need to descale your equipment a couple of times a year to ensure that this doesn't affect or create a drop in your coffee quality at home.

For example, if you're using an espresso machine at home and you water filtration isn't working correctly or needs replacing, this can severely damage your equipment and could cost a lost of money if you aren't on top of it.

The Science of Water for Coffee

But what makes good water for coffee? To really understand this, we're diving right back into the science of what water actually is.

This might sound strange, but water isn't just pure H2O. It also contains a variety of salts, minerals, and impurities.

Hard water has a higher proportion of calcium and magnesium, whereas soft water has a higher proportion of bicarbonate.

They all have an affect on the flavour and extraction capabilities of the water - in both positive and negative ways.


This is essential for coffee extraction.


This acts as a bind between flavour compounds and pulls out the juiciness from the coffee beans.

High magnesium levels increase the extraction of coffee into water and improves the taste.


This acts as a buffer, essentially controlling the pH of the water. At low levels bicarbonate can add sweetness to a coffee's flavour, but too much will make your coffee taste salty.

As you can see, these minerals are essential for extraction of the coffee.

But if the proportion of these minerals are too high, they can overwhelm the coffee and ruin the clarity, especially with lighter roasts.

However, it's not just the amount of these minerals that you have to think about, but also the balance.

The relationship between these substances will make the same coffee, brewed the same way, end up as a radically different cup.

In the book Water for Coffee by Christopher H. Hendon and Maxwell Colonna-Dashwood, they found that the total amount of mineral content in the water, up to a certain degree, is less important than the ratio between total hardness and carbonate hardness (also known as alkalinity).

Total hardness is the combined measurement of calcium and magnesium, while alkalinity is the buffering capacity of the water.

The research concluded that a 2:1 relationship is optimal for brewing balanced and flavourful coffee. Learn more about the science of hard water from our friends at Flix.

So, what water should you use?

There are a wide variety of water options available but we've summarised the most popular options you'll want to consider. 

Tap Water

While tap water is clean and perfectly fine to drink, it most definitely isn't great for brewing coffee.

Depending on where you are in the world, it can be hard or soft. As we discussed, neither of these options make perfect coffee.

Bottled Water for Coffee

There is also the option of using bottled water. We don't recommend using bottled water on a long term basis because of the environmental impact, which goes against our commitment to sustainability at Balance.

However, if you're looking to experiment to find out what bottled water for coffee is best then take our advice. Ashbeck from Tesco seems to work perfectly in terms of PH balance. 

Water Filter Units

If you're serious about your coffee, and you understand the huge impact water has on flavour, then you'll want to choose a more permanent solution.

That means investing in a professional coffee filter which will simply feed off of the mains water tap in your house. That's the same one you use for your sink, washing machine and so forth.  

There are many options available such as Brita, but we've favoured Everpure. 

What's great about these filters, is they have an adjustment dial so you can optimise the filter based on the PH value of your local water.  I

Alternative options exist also like the Peak Water.

They allow you to measure the hardness of your water and compare the results to the optimal level.

You then use their adjustable water filter jug, which allows you to decide how many of the minerals in your water are filtered out or retained.

Pretty ingenious!

Try This Experiment

We know that water is a complex subject. So if you're new to the idea of water improving your coffee why not try a little experiment?

Brew two coffees alongside each other:

1. As you usually would with tap water

2. Brew the same coffee with the same recipe using a bottled water (just do it the once - we do not condone the unnecessary use of plastics).

Ashbeck water from Tesco is reasonable for brewing coffee. Compare the taste of your coffees. Which do you prefer?

Alternatively, you can ask friends or family members to bring you some of their water - even ones who live close to you will have a slightly different level of water hardness! - or ask your local coffee shop about their water.

I am sure that a barista would be happy to give you some of their water to try.

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