Why Water Quality Could Be the Hidden Reason Your Coffee Tastes Off

You’ve dialed in the perfect grind. Your espresso machine is preheated, your beans are fresh, and your tamp was spot-on. But the final shot tastes flat, harsh, or just… wrong.

If this scenario feels familiar, there’s a high chance the culprit isn’t your technique or your beans—it’s your water.

Most people don’t realize it, but water is the main ingredient in coffee. In fact, espresso is about 90% water, and filter coffee? Over 98%. That means if your water is off, your coffee will be too—no matter how great your gear or how skilled your technique.

In this article, we’re diving deep into why water quality is one of the most overlooked elements in barista culture, how it directly affects taste and equipment, and how you can fix it whether you’re working in a café or brewing at home.

The Role of Water in Coffee Extraction

When brewing coffee, water acts as a solvent. It pulls out acids, sugars, oils, and other flavor compounds from the coffee grounds. But water doesn’t just extract—it also interacts with those compounds based on its mineral content and chemical makeup.

Here’s the breakdown:

• Hard water (high in minerals like calcium and magnesium) can extract too much, often leading to dull or bitter brews.
• Soft water (low in minerals) might not extract enough, producing weak or sour coffee.
• Unfiltered tap water might contain chlorine, sediment, or even metals that interfere with flavor and crema.

The key is balance—just enough mineral content to support full, sweet extraction, without overpowering or muting the coffee’s natural profile.

What’s in Your Water?

Let’s look at the most relevant components:

1. Total Dissolved Solids (TDS)

TDS measures everything dissolved in your water—mostly minerals. Ideal TDS for coffee is 75–150 ppm (parts per million).

Too low = under-extraction
Too high = flat, bitter flavor

2. General Hardness (GH)

This refers to the amount of calcium and magnesium, the key minerals that affect extraction. Ideal range: 40–70 ppm

These minerals help extract flavor, but too much can lead to heavy, unbalanced cups.

3. Carbonate Hardness (KH)

Also called alkalinity, KH buffers acidity. Ideal range: 40 ppm.
Too much = dull coffee
Too little = overly sharp acidity

4. pH Level

Neutral pH (around 7) is best. Water that’s too acidic or too basic can skew your extraction or react poorly with your equipment.

5. Chlorine and Chloramine

Even small amounts of chlorine can ruin coffee’s aroma and taste. These chemicals are often found in tap water and should always be removed with filtration.

Signs That Your Water Is Hurting Your Coffee

Not sure if your water is the issue? Here are some clues:

• You brew the same coffee as your favorite café, but it tastes totally different
• You notice inconsistent flavor throughout the day or week
• Your espresso lacks crema or tastes overly flat despite good prep
• Your equipment builds up scale quickly, even with regular cleaning
• Your coffee tastes like metal, plastic, or chemicals

If any of these sound familiar, water is likely the silent saboteur.

How to Test Your Water

1. Use a Water Testing Kit

Affordable and easy to use, these kits give you TDS, hardness, pH, and more. Great for home baristas.

2. Ask Your Local Water Utility

Many cities publish detailed water reports. Look for mineral content, pH, and chlorine levels.

3. Use a TDS Meter

It won’t give full data, but it’s a fast way to check if your water falls within the ideal range.

Once you know what you’re working with, you can start improving it.

How to Fix Bad Water for Coffee

1. Filter It

The simplest and fastest step. A carbon-based filter (like Brita or Soma) removes chlorine and some sediment. For better results, go with systems like:

• Third Wave Water mineral packets
• ZeroWater (followed by remineralization)
• Reverse osmosis systems with re-mineralization stages

Avoid using pure distilled water—it lacks essential minerals for proper extraction and can damage espresso machines over time.

2. Build Your Own Brew Water

Yes, really. Many baristas mix distilled or RO water with measured minerals for full control. Third Wave Water makes this easy with pre-formulated packets.

Ideal DIY recipe:

• Start with distilled or RO water
• Add minerals to reach 50 ppm calcium, 10 ppm magnesium, 40 ppm alkalinity
• Shake well and use within a few days

It might sound geeky, but the flavor difference is real.

3. Use Bottled Water (If Needed)

Some bottled waters are great for coffee, others aren’t.

Good options:

• Crystal Geyser
• Volvic
• Nestlé Pure Life (in some regions)

Avoid:

• Evian (too high in minerals)
• Dasani or Aquafina (often too soft)

Protecting Your Equipment

Bad water doesn’t just hurt flavor—it destroys machines. High mineral content leads to scale buildup, which can clog boilers, damage heating elements, and reduce pressure. This affects both espresso machines and kettles.

Using filtered or properly balanced water:

• Extends your machine’s lifespan
• Reduces cleaning frequency
• Keeps your coffee tasting consistent

If you’re investing in good gear, investing in good water is just as important.

FAQs

Do I need to obsess over water if I only brew at home?
Not obsess—but be aware. Even basic filtration can dramatically improve taste. If you’re investing in beans and gear, water should match that standard.

Can I use distilled water in my espresso machine?
No. It lacks minerals needed for taste and conductivity, and can damage boilers or sensors. Always use remineralized or balanced water.

What’s better: filter or bottled?
Filtered is more sustainable and cost-effective. Bottled is a good backup, but not ideal long term unless you find the right brand.

Why does coffee taste better in some cafés even when using the same beans?
Water is often the difference. High-end cafés control water quality carefully and build it to spec.

How do I know if I’ve hit the right water profile?
When your coffee tastes more expressive, clear, and balanced across different methods—you’ll know. It’s like taking the lid off the flavor.

Final Thoughts

You can master your tamp, time your shots perfectly, and use the freshest beans available—but if your water isn’t right, you’ll always be fighting an invisible enemy. Water is the most overlooked, yet most influential, ingredient in every cup of coffee you make.

The good news? Once you start taking control of your water, everything else gets easier. Your flavors become more predictable. Your gear stays cleaner. And your skills as a barista level up in a way most beginners never experience.

So the next time your espresso tastes “off,” don’t just adjust your grinder. Ask yourself: what’s in my water?