Water makes up 98% of your cup. The other 2% is coffee.
So yes. The water you use matters. A lot.
But most people focus on beans, grinders, and brewing technique while using whatever comes out of the tap. If your coffee tastes flat, bitter, or just off, your water might be the reason.
Here's what actually determines whether your water is good for coffee.
The three things that matter
The Specialty Coffee Association (SCA) Water Quality Handbook identifies two core parameters that drive flavor and extraction: alkalinity and total hardness. pH rounds out the picture as a safety and balance check.
Everything else (including TDS) is secondary. More on that in a moment.
1. Alkalinity: the most important factor
Alkalinity measures your water's ability to neutralize acids.
Coffee is naturally acidic. Those acids carry much of what makes specialty coffee taste bright, fruity, and complex. Alkalinity acts as a buffer: it absorbs some of those acids before they reach your palate.
The problem is balance.
- Too much alkalinity neutralizes the good acids. The result is a flat, dull cup: no brightness, no life.
- Too little alkalinity (below 40 ppm) and the acids are completely unrestrained. Coffee tastes sharp and sour. Equipment also corrodes faster.
SCA ideal range: 40-75 ppm (as CaCO₃)
2. Total hardness: the extraction engine
Hardness comes from dissolved calcium and magnesium minerals.
These minerals aren't just passive passengers. They actively bind to flavor compounds in the coffee grounds and pull them into the water. No minerals, no extraction. That's why distilled water makes terrible coffee: it's too pure. It has nothing to work with.
- Too soft (low hardness): coffee is weak, watery, under-extracted. Sour and thin.
- Too hard (high hardness): extraction becomes uneven, subtle flavors get suppressed. Limescale builds up in your equipment faster.
SCA ideal range: 50-175 ppm total hardness
One important rule from the SCA handbook: total hardness should always be greater than alkalinity. When alkalinity exceeds hardness, the water's buffering capacity overwhelms the minerals doing the extraction work, and cup quality suffers.
3. pH: safety and balance
pH tells you whether your water is acidic or basic.
The SCA recommends a pH between 6.5 and 7.5, with 7.0 as the target. This range is neutral enough to not interfere with flavor and safe for the metals in your equipment.
For most filtered or bottled water, pH is already in range. It's rarely the problem, but it's worth knowing.
What about chlorine?
The SCA standard is unambiguous: no detectable chlorine. None.
A basic carbon filter (like a Brita) removes chlorine effectively. If you're using tap water without any filtration, this is the first and easiest fix.
Does water brand matter?
Some bottled mineral waters fall naturally within the SCA ideal ranges. Most don't; they're either too hard, too alkaline, or both.
The only way to know is to check the label. Look for:
- Alkalinity (or bicarbonate/HCO₃): ideally 40-75 ppm
- Total hardness (or calcium + magnesium): ideally 50-175 ppm
- pH: 6.5-7.5
The quick summary
| Parameter | Ideal range | Why it matters |
|---|---|---|
| Alkalinity | 40-75 ppm | Controls acidity balance in the cup |
| Total hardness | 50-175 ppm | Drives extraction of flavor compounds |
| pH | 6.5-7.5 | Safety and equipment protection |
| Chlorine | None detectable | Kills aroma |
Good water for coffee isn't about purity. It's about mineral balance: specifically, the relationship between alkalinity and hardness.
Find out if your water is ruining your coffee
Download Café com Água and evaluate your water quality based on SCA standards. Free on Google Play.
Download Café com Água