Baristas often focus on grind size, dose, and brew ratios—but one variable is frequently underestimated: water quality. Since water makes up about 98% of a cup of coffee, its composition can drastically alter flavor, texture, and balance.
Using the wrong kind of water can ruin even the highest-quality beans. For a barista, mastering water is just as important as choosing the right coffee or adjusting espresso variables. It’s a hidden factor that separates good cafés from great ones.
What Is in Your Water?
Water is never just H₂O. It usually contains minerals, chlorine, salts, and organic compounds, all of which affect extraction and flavor.
The most relevant components in brewing are:
- Calcium and magnesium: These are the primary hardness minerals. They help extract flavorful compounds from coffee grounds.
- Carbonates (bicarbonate): Act as buffers. Too much can flatten acidity and clarity.
- Chlorine or chloramine: Used in municipal water. They create unpleasant chemical flavors.
- TDS (Total Dissolved Solids): Measures all dissolved substances in water. High or low TDS affects strength and mouthfeel.
Good brewing water balances hardness and alkalinity to extract flavor without overdoing bitterness or muting acidity.
The Ideal Water Composition for Coffee
The Specialty Coffee Association (SCA) provides a standard water profile for optimal brewing. According to their guidelines:
- Calcium hardness: 50–70 ppm (as CaCO₃)
- Magnesium hardness: 10–30 ppm
- Total hardness: 50–175 ppm
- Alkalinity: 40 ppm
- pH level: 6.5 to 7.5
- TDS: 75–250 ppm
If your water is outside of these ranges, your coffee will likely taste off. Bitterness, dullness, and inconsistent extraction often trace back to water—not the coffee or barista.
Soft Water vs. Hard Water: What’s the Difference?
Hard water contains high levels of calcium and magnesium. It extracts flavors aggressively, sometimes leading to over-extraction, bitterness, or harshness. However, moderate hardness helps pull out desirable flavors and improve body.
Soft water, on the other hand, lacks the minerals needed for full extraction. The result can be weak, sour, or hollow coffee. Soft water may also cause uneven extractions, especially in espresso.
For baristas, water hardness affects not just taste, but also machine health. Hard water causes limescale buildup in boilers, leading to costly repairs if not managed.
The Problem With Tap Water
Most tap water is treated for safety, not flavor. It often contains:
- Chlorine or chloramine: Adds metallic or chemical notes.
- Sediments or organic compounds: Cloud the flavor clarity.
- Inconsistent mineral content: Varies by location and season.
Even if your café uses filtered water, it’s important to test it regularly. A small change in municipal water treatment can drastically affect espresso quality.
How to Test Your Water
As a professional barista, you should test water monthly—especially if you’re noticing shifts in flavor or extraction behavior. Use tools like:
- TDS meters: Measure total dissolved solids.
- Water hardness test strips: Give a quick reading of calcium/magnesium levels.
- pH meters: Check if your water is acidic or alkaline.
You can also send water samples to a lab or use coffee-specific water test kits. Some roasters even include recommended water specs for their beans.
Filtration Systems: What Your Café Might Need
There are several types of filtration systems, each with pros and cons depending on your water source:
- Carbon filters: Remove chlorine and bad taste. Not sufficient for minerals.
- Reverse osmosis (RO): Removes almost everything, including minerals. Must be remineralized to work for coffee.
- Softening filters: Remove calcium and magnesium. Often used in areas with hard water.
- Blending systems: Combine filtered water with a controlled amount of tap water to reach ideal mineral levels.
Speak with a water technician or roaster to determine the best system for your region. Proper installation and maintenance are essential.
Bottled Water: A Temporary Solution
In small operations or pop-ups, baristas sometimes use bottled water for consistency. While this can improve results short term, it’s expensive and environmentally unsustainable long term.
If you go this route, choose bottled waters with moderate mineral content, like:
- Third Wave Water: Additives that recreate SCA-standard brewing water.
- Crystal Geyser or Volvic: Often used for cuppings and competitions.
Avoid distilled or deionized water—these lack minerals and produce flat, poor extractions.
Water Temperature and Its Role in Brewing
Beyond chemistry, temperature also affects how water extracts coffee. The standard brew temperature range is:
- 90–96°C (195–205°F)
Lower temps extract fewer bitter compounds but may underdevelop the cup. Higher temps extract more oils, acids, and bitters.
Use:
- 90–92°C for light roasts with high acidity.
- 93–95°C for medium roasts or balanced profiles.
- 95–96°C for dark roasts or immersion brews.
Baristas using variable temperature kettles or PID-controlled machines can fine-tune this based on the coffee at hand.
Espresso Machines and Water Quality
Espresso machines are especially vulnerable to poor water. Hard water causes:
- Limescale buildup in boilers and pipes.
- Reduced steam pressure and inconsistent temperatures.
- Mechanical failure of solenoids, group heads, and flow meters.
Use water softeners, pre-filters, and regular descaling to extend equipment life. Many manufacturers void warranties if poor water is used—so baristas must advocate for quality control.
Water and Coffee Competitions
At events like the World Barista Championship, water is a controlled element. Competitors often create custom mineral blends to suit their coffee.
For example, higher magnesium content can boost sweetness and mouthfeel, while lowering calcium can reduce bitterness. Understanding how minerals interact with flavor allows baristas to build water profiles like recipes.
This level of control isn’t just for competition—ambitious cafés use it to fine-tune offerings and stand out in a competitive market.
Communicating With Customers About Water
Most customers don’t realize water affects flavor. This is a chance to educate gently:
- “We filter our water to match the coffee’s mineral needs.”
- “Your coffee may taste different at home due to your tap water.”
- “Bitter or dull flavors are often caused by water—not over-roasting.”
Offering water education adds value to your service and reinforces your expertise as a barista.
Final Thoughts: Water Is Your Hidden Ingredient
You can’t make great coffee with bad water. As a barista, understanding and controlling water is as critical as choosing quality beans or dialing in espresso.
Don’t ignore it. Test it. Adjust it. Learn from it.
By mastering water, you unlock the full potential of your coffee—and deliver an experience that’s clean, vibrant, and worthy of the craft.
Artur is a coffee enthusiast and content creator passionate about barista techniques and coffee culture. With a sharp eye for detail and a love for learning, he shares practical tips, brewing guides, and gear insights to help readers elevate their coffee experience — from home brewers to aspiring professionals.