Water quality and its influence on coffee quality

The decisive factor for coffee quality in the cup

Water is the most underrated ingredient in coffee – even though it makes up over 90% of every cup. While beans, roasting, and brewing techniques are often the focus, the chemical composition of the water determines whether a coffee tastes complex, balanced, and clear, or flat, bitter, and unbalanced.

This article shows why water is not just a carrier medium, but an active factor influencing taste , which parameters are truly relevant, and how water quality affects both the sensory experience in the cup and the lifespan of machines and filter systems .

1. Water as an active component of coffee extraction

When brewing coffee, water acts as a solvent. It selectively extracts acids, sugars, lipids, and bitter substances from the coffee grounds. Which of these substances are dissolved, and to what extent, depends directly on the mineral content and buffering capacity of the water.

Certain minerals play a key role in this:

• Magnesium supports the extraction of fruity and sweet aroma components.

• Calcium enhances body and mouthfeel.

• Bicarbonate buffers acids and influences the balance.

• Sodium can enhance the perception of sweetness in very small amounts.

An unbalanced water profile can disrupt these mechanisms – with immediate consequences for the taste, clarity and structure of the coffee.

2. The most important water parameters for good coffee

Not all drinking water is automatically suitable for coffee. A few clearly defined parameters are crucial:

• Total hardness

• Alkalinity (carbonate hardness)

• PH value

• Total Mineralisation (TDS)

• calcium to magnesium ratio

• Absence of foreign substances such as chlorine or iron

Balanced water ensures stable extraction, reproducible results and sensory clarity – regardless of whether espresso or filter coffee is being prepared.

3. Visual overview: Optimal water parameters for coffee

The following infographic clearly summarizes the ideal water parameters for espresso, filter coffee and fully automatic coffee machines:

In short:

• TDS (Total Dissolved Solids):
  Optimal range between 75–250 mg/L – below this, coffee tastes flat, above this it often tastes bitter.

• PH value:
  Ideally slightly acidic to neutral (approx. 6.6–7.5)

• Water hardness:
  Recommended 2–6 °dH , depending on the brewing method

• Minerals:
  Balanced ratio of magnesium and calcium

• Foreign substances:
  Chlorine and organic substances should be removed.

4. Sensory effects of contaminated water

The sensory consequences of unsuitable water quality are clearly noticeable:

Water that is too soft

• Underextraction

• Thin body

• Overly pronounced, sharp acids

Water that is too hard

• Subdued acids

• Bitterness and dryness

• Less aromatic clarity

Optimally balanced water

• Balanced acidity

• Clearly defined sweetness

• Long, clean aftertaste

Especially with high-quality coffees, water determines whether the origin and roasting can be experienced sensorially.

5. Water quality and its effects on coffee machines

Besides the taste, water also significantly influences the technique behind coffee :

Limescale formation

Hard water leads to deposits in:

• boiler

• heat exchangers

• Valves and pipes

This impairs temperature stability, increases energy consumption and shortens the machine's lifespan.

corrosion

Extremely soft or demineralized water can:

• Attacking metallic components

• Damage to sensors and seals

Solution: controlled water treatment

Combining professional solutions:

• Activated carbon filtration (against chlorine & odors)

• Water softening or reverse osmosis

• Targeted remineralization

This not only improves the coffee quality but also protects the machine in the long term.

6. Water profiles according to brewing method

These profiles serve as a starting point and can be fine-tuned depending on the bean, roast, and personal preference.

7. Conclusion: Water determines quality

Water is not a supporting actor, but the decisive director in the coffee brewing process. It influences:

• the extraction of flavorings

• the sensory balance in the cup

• the reproducibility of the results

• the maintenance and lifespan of the machine

Anyone who wants to consistently prepare excellent coffee – whether in a professional setting or at home – cannot avoid consciously addressing water quality .

If you were interested in our blog article and would like to learn more about this topic in greater detail, you can delve deeper into this exciting subject and read our white paper "The Importance of Water Quality for Coffee Quality, Extraction and Machine Technology".

Sources & technical foundations

• Coffee Makers Switzerland – Coffee Water & Water Parameters

• Specialty Coffee Association (SCA) – Water Standards

• Goran Huber Coffee Institute (AT) – The Importance of Water for Coffee

• Technical publications on coffee extraction and water chemistry