When it comes to brewing coffee, most people focus on the beans, the roast, or the brewing method. But there’s one element that often gets overlooked—water. Since a cup of coffee is roughly 98% water, the quality, temperature, and mineral content of your water can dramatically affect the taste of your brew.
In this article, we’ll explore how water plays a critical role in making great coffee, what kind of water you should use, and practical tips to improve your daily brew by simply changing how you think about water.
Why Water Matters in Coffee Brewing
Water does more than just dissolve coffee grounds. It extracts flavor compounds, aromas, and oils from the coffee beans. Depending on the water’s mineral content, temperature, and purity, it can:
- Over-extract or under-extract the coffee
- Introduce off-flavors
- Flatten the aroma
- Unbalance the cup
Even if you use the highest-quality beans and the best brewing gear, using poor-quality water can result in disappointing coffee.
What Is the Best Water for Coffee?
The best water for coffee is clean, fresh, and balanced in mineral content—not too hard, not too soft. According to the Specialty Coffee Association (SCA), ideal brewing water should have:
- Total dissolved solids (TDS): 75–250 ppm
- Calcium hardness: 50–175 ppm
- Alkalinity: 40–75 ppm
- pH level: Between 6.5 and 7.5
That might sound technical, but in simple terms: your water should be neither too hard nor too soft, with enough minerals to extract flavors but not so many that it overwhelms them.
Hard Water vs. Soft Water
Hard water contains high levels of calcium and magnesium. While these minerals can help extract flavor, too much can lead to:
- Over-extraction (resulting in bitter, dull coffee)
- Scale build-up in coffee machines
Soft water, on the other hand, has very few minerals. While it’s less likely to cause scale, it can:
- Under-extract coffee (resulting in sour, weak coffee)
- Produce flat or lifeless flavor
If your tap water is too soft or too hard, consider filtering it or using bottled water formulated for coffee.
Should You Use Tap Water?
It depends on your local water supply.
If your tap water tastes clean and neutral, it might be just fine for brewing. But if it has:
- A chlorine smell
- Metallic or earthy flavors
- Cloudiness or sediment
Then it’s best to avoid it or filter it. Chlorine and other chemicals not only affect flavor but can interfere with proper extraction.
You can use a carbon filter (like a Brita pitcher) to remove most unwanted tastes and odors from tap water. However, keep in mind that basic filters don’t remove minerals—they mainly improve taste.
Bottled Water: A Safe Middle Ground?
Many coffee lovers opt for bottled spring water or specially formulated water for coffee brewing.
Look for bottled waters with balanced mineral content, ideally between 75–150 ppm of TDS. Avoid distilled or “purified” waters that have no minerals at all, as these won’t extract coffee properly and may result in a sour, underdeveloped brew.
Some brands even sell coffee brewing water kits, where you add minerals to distilled water to achieve the perfect balance.
Water Temperature Matters Too
Besides quality, temperature is another important factor.
The ideal brewing temperature for most methods (drip, pour-over, French press) is:
- 195°F to 205°F (90°C to 96°C)
Too hot? You risk over-extraction—bitter, burnt flavors.
Too cool? You under-extract—weak, sour coffee.
If you don’t have a thermometer, bring water to a boil and then let it rest for about 30 seconds before pouring. This usually gets you into the ideal range.
Water-to-Coffee Ratio: Don’t Guess
Another water-related factor that impacts taste is the brew ratio. Using too much or too little water can make your coffee taste off.
A common guideline is:
- 1:15 to 1:17 ratio (1 gram of coffee to 15–17 grams of water)
For example, for a standard 300 ml cup, you’d use around 18 to 20 grams of coffee. Use a scale for accuracy if possible.
What About Espresso?
In espresso, water quality becomes even more critical. Since espresso is highly concentrated, any off-flavor in the water becomes exaggerated in the final cup.
Use filtered water with good mineral balance to ensure:
- Proper pressure and extraction
- Balanced crema
- No metallic or sour notes
Also, hard water can quickly scale up your espresso machine, affecting performance and longevity. Descale regularly and use filtered or softened water whenever possible.
Practical Tips for Better Water in Your Coffee Routine
- Test your tap water: Use a TDS meter or contact your water provider.
- Taste your water: If it tastes off, your coffee will too.
- Use a water filter: A simple carbon filter can improve flavor and remove chlorine.
- Avoid distilled or demineralized water: They’re too “empty” to extract coffee well.
- Consider bottled spring water: If your tap water isn’t ideal.
- Monitor brewing temperature: Let boiled water cool slightly before brewing.
- Adjust based on method: Different brewing techniques may respond differently to water types.
Final Thoughts: Don’t Let Water Be the Weak Link
Water is more than a vehicle for your coffee—it’s the foundation of every cup. Once you understand how water affects extraction, taste, and consistency, you can take your home brewing to the next level.
You don’t need to be a scientist or use fancy lab equipment. Start by making small adjustments: use filtered water, check your temperature, and experiment with brew ratios. Over time, you’ll notice your coffee tasting cleaner, brighter, and more balanced.
Remember: great coffee isn’t just about the beans—it’s about everything that goes into the cup, including the water.