Around 4–8 °dH total hardness and a pH of around 7. The SCA recommends 50–175 ppm total hardness and 40–70 ppm carbonate hardness. German tap water is usually too hard — Berlin's water sits at 14–22 °dH.

What is the ideal water hardness for coffee?

Around 4–8 °dH total hardness and a pH of around 7. The SCA recommends 50–175 ppm total hardness and 40–70 ppm carbonate hardness. German tap water is usually too hard — Berlin’s water sits at 14–22 °dH.

Why that is

The Specialty Coffee Association (SCA) has established clear recommendations for brewing water, based on extensive sensory testing. The target values:

• Total Hardness: 50–175 ppm (target value 150 ppm), which is roughly 3–10 °dH
• Carbonate Hardness: 40–70 ppm (target value 40 ppm)
• pH Level: 6.5–7.5 (target value 7.0)
• Chlorine: 0 mg/L

These numbers aren’t marketing — they’re based on how minerals influence flavor extraction. Calcium and magnesium help dissolve flavor compounds from the coffee grounds. Too few minerals mean under-extraction: thin, bland coffee. Too many overwhelm the cup and mask delicate aromas.

Carbonate hardness is the buffer that neutralizes acids in coffee. High carbonate hardness (typical for German tap water) swallows up the vibrant acidity that characterizes specialty coffee. The result: a flat, dull coffee devoid of fruitiness.

On average, German tap water is around 16 °dH — far above the ideal range. There are huge regional differences: Northern Germany and Berlin are particularly hard (14–22 °dH), while parts of Bavaria and the Black Forest are significantly softer. You can check your local water hardness with your water provider or measure it yourself using test strips from the pharmacy.

In Berlin-Lichtenberg, water hardness is 14–18 °dH depending on the supply zone. That counts as “hard” on the German scale and is way over the SCA ideal. Without filtration, your coffee is missing the fruity and floral notes that good beans naturally possess.

Knowing your water hardness lets you take deliberate action: pitcher filters for moderate improvement, under-sink filters for precise control, or mineral concentrates added to distilled water for perfect profiles.

In practice at Green Wall Coffee

At Sophienstraße 27, we filter our Berlin tap water down to about 5–6 °dH. The difference was instantly noticeable when we installed the filter — same beans, noticeably more clarity and fruitiness in the cup. As a first step, I always advise guests: check your water hardness. Test strips cost a few euros. If you’re over 10 °dH, you will benefit from a filter.

Related questions

• How important is water quality for good coffee?
• Do I need a water filter for my coffee machine?
• Brita or BWT: Which water filter is better for coffee?

You can find more in-depth information in the article How to make perfect espresso. Or drop by Sophienstraße 27 — Mon–Fri 8am–5pm, Sat 10am–5pm.