Water makes up more than 98% of your cup, yet it’s often the most overlooked part of the brewing process. From clarity and sweetness to acidity and balance, how water affects coffee flavor is one of the most important (and misunderstood) factors in brewing truly great coffee.
In this Evans Brothers Coffee article, we’re breaking down why water quality matters, what’s actually happening at a chemical level during extraction, and how small adjustments to your water can unlock more of the flavors your roaster intended.
Why water matters more than most people realize
Water is easy to overlook when brewing coffee, but it’s doing much of the heavy lifting in your cup. Since coffee is almost entirely water, the quality of what you brew with can have a direct impact on how your coffee tastes, no matter how good the beans are.
Coffee is mostly water (and that changes everything)
Daniel Gunter, Director of Coffee Quality at Evans Brothers Coffee, says, “Water quality makes a bigger impact than most people realize because coffee is mostly water.”
When you break it down, the numbers make it hard to ignore:
- Drip coffee is about 98.5% water
- Espresso is still roughly 90% water
With that much water involved, any off flavors or odors will show up immediately in the cup. “If your water isn’t good, your coffee won’t be either,” Daniel explains.
Clean water lets coffee do its thing
The goal isn’t perfect water, it’s water that gets out of the way. Clean, neutral-tasting water allows the coffee itself to shine. Daniel notes, “If water is free from odors and other taints, we can produce a pleasant cup from any high quality, well-roasted coffee.”
Rather than chasing a single “best” recipe, it helps to think of water as something that interacts with each coffee a little differently. “There is no best water for coffee,” Daniel says, but filtered, reasonably soft water tends to highlight sweetness and nuance more consistently.
A few general patterns show up again and again:
- Softer water often brings out clarity and sweetness
- Different roast levels respond differently to the same water
- “The ‘best’ water for a dark roast may not be the ‘best’ water for a light roast,” Daniel adds
Paying attention to your water doesn’t have to be technical or intimidating. It’s simply one of the easiest ways to move from an okay cup to one that feels balanced, intentional, and true to how the coffee was meant to taste.
The role of minerals in coffee brewing
Once you start paying attention to water, minerals are usually the next piece of the puzzle. They’re invisible, easy to forget, and quietly responsible for why one cup tastes sweet and lively while another tastes flat or harsh.
The two mineral factors that matter most
According to Daniel, brewing water can get complicated quickly, but two factors matter more than most: General Hardness (GH) and Carbonate Hardness (KH). Daniel says that this explanation is a “more-complex-than-I’d-like” simple version of how minerals affect coffee.
General Hardness (GH) usually comes from calcium and magnesium, and it plays a big role in extraction.
- Helps pull flavor from coffee grounds
- Contributes to sweetness and texture
- Too much can cause harsh or bitter flavors
- Can lead to mineral scale buildup in brewing equipment
- A common target range is 40–100 ppm
Carbonate Hardness (KH), also called alkalinity, affects how acidity shows up in the cup.
- Acts as a buffer for acidity
- Too little can make coffee taste sharp or sour
- Too much can leave the cup flat, muddled, or gritty
- A typical target range is 20–80 ppm
How minerals shape flavor
These two mineral components work together to shape how coffee tastes. GH helps extract flavor, while KH controls how that extraction feels on your palate. When they’re in balance, coffee tends to taste sweeter, clearer, and more complete.
To simplify it even further, Daniel explains that softer water often highlights sweetness and complexity, while harder water can mute flavors as mineral content increases. This is why the same coffee can taste vibrant at one home and dull at another, even when the brew method is identical.
Minerals don’t need to be something you obsess over, but understanding their role helps explain why water isn’t just water. It’s an active ingredient that decides which flavors get pulled forward, and which ones stay hidden.
How water interacts with roast level and origin
Once you start paying attention to your water, it becomes pretty clear why one setup doesn’t work for every coffee. Roast level, origin, and water chemistry all influence each other, and sometimes a small tweak is all it takes to make a coffee click.
Using brew ratio to work with your water
One of the easiest ways to adapt is by adjusting your brew ratio.
“Altering your brew ratio depending on roast level or the water used can be a great tool to get the best out of your beans,” Daniel shares. Brew ratio is simply how much coffee you’re using compared to how much water.
For example:
- 20g coffee to 300ml water (1:15) will taste stronger and more concentrated
- 20g coffee to 360ml water (1:18) will feel lighter and more open
Neither is right or wrong, it just depends on the coffee and the water you’re working with.
Letting water and coffee balance each other
Water with more buffering power can handle more intensity. “The more concentrated you brew your coffee, the more KH you may like in order to balance the acidity present in the cup,” Daniel explains. Another way he frames it is that if your water is harder or has higher alkalinity, brewing a bit stronger can help the coffee really sing.
With softer water, things tend to open up more easily. “If using soft water, you can generally brew a longer or ‘weaker’ ratio with good results,” Daniel says. In those cups, “sweetness, body, and complexity will come through nicely,” which is often where light roast coffees feel their most expressive, showing off fruity, floral, and delicate notes.
Roast level, density, and a little experimentation
Lighter roast coffees are often denser, which means they sometimes need a little extra help during extraction. “More water equals more extracting power,” Daniel says, so lighter roasts often benefit from more water than darker coffees.
If you brew that same coffee with much harder water, you may notice you need to tighten up the ratio to bring out sweetness and clarity. Most people don’t have full control over their water, and that’s okay. Daniel points out, “If you can figure out how hard your water is, then that can help to guide you.”
At the end of the day, this is less about chasing perfection and more about paying attention. A small change in water or ratio can be the difference between a cup that’s just fine and one that really shows you what that coffee has to offer.
Common water mistakes home brewers make
When coffee at home tastes off, most people assume the beans or the brew method are to blame. In reality, the issue is often much simpler, and it sometimes starts with the water.
Not using filtered water
The most common mistake Daniel sees is skipping filtration altogether. Many tap waters contain chlorine or other impurities that may not seem obvious on their own, but they show up clearly once coffee is brewed.
Daniel says plainly, “If your water doesn’t taste like chlorine, your coffee won’t taste like chlorine either.” Even a basic home filter, like a Brita, can remove off flavors and make a noticeable difference right away.
Overlooking hard water issues
For people on well water, the challenge is often hardness rather than taste. Hard water doesn’t always smell or taste bad, but it can still cause problems.
According to Daniel, it can lead to:
- Mineral scale buildup in brewing equipment
- More muted, less expressive cups of coffee
While well water may seem fine at first glance, excessive minerals can quietly dull flavor over time.
Thinking fixes have to be complicated
The good news is that improving your water doesn’t have to be expensive or intimidating. Daniel recommends starting simple:
- Use a basic filter pitcher or under-sink filter
- Pay attention to how your water tastes before brewing
For those who want to go a step further, using distilled or water with added minerals is a popular option. “There are some great off-the-shelf solutions,” Daniel notes, like mineral packets that can be added to a gallon of water to create more balanced brewing water.
For curious brewers who enjoy experimenting, there are also deeper resources available for creating custom water recipes at home. These options aren’t necessary for great coffee, but they can be a fun way to learn how water shapes flavor.
Simple ways to improve your brewing water at home
Improving your brewing water doesn’t have to turn into a science project. In fact, a few small, approachable changes can make a big difference in how your coffee tastes day to day.
Start with water that tastes good
If there’s one place to begin, it’s this. “Use filtered water! Or at least make sure it tastes good to start and your brewing life becomes much easier,” Daniel recommends. If you wouldn’t enjoy drinking the water on its own, it’s unlikely to make great coffee.
A basic filter can help by:
- Removing chlorine and off flavors
- Improving clarity and balance in the cup
- Creating more consistent results from brew to brew
Let water support the coffee
The goal of good brewing water isn’t to add flavor; it’s to support the coffee. When water is clean and balanced, it allows sweetness, acidity, and nuance to show up naturally without fighting against unwanted tastes or mineral extremes.
At the end of the day, paying attention to your water is one of the easiest ways to improve your coffee without changing your beans, grinder, or brew method. Start with water that tastes good, and let the coffee do the rest.
How water affects coffee flavor in every cup
Understanding how water affects coffee flavor can completely change the way you think about brewing. You can buy great beans and use the perfect brew method, but if your water isn’t right, the coffee will never fully show up the way it’s meant to. Paying attention to your water is one of the simplest ways to get closer to the coffee your roaster worked so hard to create.
Written by Allie Drinkward