The right water for espresso: a guide for Switzerland
Why water matters so much
An espresso is around 90 % water. Even so, it is often treated as an afterthought: people pay attention to the beans, the grinder and the machine, but hardly to what comes out of the tap. Yet water decides twice: on the taste in the cup and on the lifetime of your machine.
Water that is too hard scales up the boiler, heating element and valves and makes the coffee flat. Water that is too soft or fully demineralised tastes sour and empty and can attack metal parts. The right water lies in between. In this guide you will find out which values are ideal, how to find out the hardness of your tap water and which treatment is worthwhile for you.
The ideal water for espresso
The Specialty Coffee Association (SCA) has set reference values for coffee water. In Switzerland, hardness is stated in French degrees (°fH). One °fH corresponds to 10 mg/L of calcium carbonate – which makes international values easy to convert.
| Value | Target | Acceptable range | In °fH |
|---|---|---|---|
| Calcium hardness | 68 mg/L | 17–85 mg/L | target about 7 °fH, range about 2–8.5 °fH |
| Alkalinity (carbonate hardness) | around 40 mg/L | – | about 4 °fH |
| Dissolved solids (TDS) | 150 mg/L | 75–250 mg/L | – |
| pH | 7.0 | 6.5–7.5 | – |
| Sodium | around 10 mg/L | – | – |
| Chlorine | 0 | – | – |
Source: SCAA water standard (2009) for coffee water.
The two most important values are hardness and alkalinity:
- Total hardness (calcium and magnesium) helps extract the aromas from the coffee. Magnesium is considered particularly good for fruity, clear aromas.
- Alkalinity (carbonate hardness) buffers the acidity in the coffee. If it is too high, the espresso tastes flat and chalky and the machine scales up quickly. If it is too low, it becomes sharp and sour.
Rule of thumb for portafilter machines: a total hardness of about 5 to 8 °fH and a carbonate hardness of about 3 to 5 °fH are a good compromise between taste and protection against scale. Many Swiss tap waters are well above this.
How hard is your water? Here is how to find out
Water hardness in Switzerland varies greatly from place to place. It depends on the rock the water flows through and whether it comes from groundwater, springs or a lake.
Where to find the hardness of your tap water:
- www.trinkwasser.ch: the platform of the SVGW (Swiss Gas and Water Association) lists the water quality of many Swiss municipalities.
- Your municipality or water supplier: water suppliers regularly publish the water hardness, usually on their website or in the municipal newsletter.
- Test strips: a strip costing a few francs shows the total hardness right at the tap. For carbonate hardness there are drop tests, for example from BWT.
The six hardness levels in Switzerland:
| Level | Total hardness | For espresso |
|---|---|---|
| very soft | 0–7 °fH | ideal to rather too soft |
| soft | 7–15 °fH | good, light filtering can make sense |
| medium hard | 15–25 °fH | filter recommended |
| fairly hard | 25–32 °fH | filter needed |
| hard | 32–42 °fH | filter essential, short change intervals |
| very hard | over 42 °fH | filter essential, possibly reverse osmosis |
Classification according to the SVGW.
Typical values by region:
| Region | Typical hardness |
|---|---|
| Alps and southern side of the Alps (Graubünden, Valais, Ticino) | rather soft |
| Pre-Alps and large parts of western Switzerland | medium hard |
| Central Plateau, Central Switzerland, north-eastern Switzerland and the Jura | fairly hard to very hard |
| Example: city of Zurich (mainly lake water) | on average about 16 °fH, carbonate hardness about 14 °fH |
| Example: Heimberg BE (groundwater) | about 19 °fH |
Values vary widely within a region, so always check for your own municipality. Important for espresso: even tap water that is "soft" by Swiss classification is often still above the target range of about 5 to 8 °fH.
Bottled water: which is suitable?
For machines with a water tank, many people reach for mineral water. That can work well – but only with the right one. Many mineral waters are considerably harder than tap water.
| Water | Total hardness | Carbonate hardness | Suitability for espresso |
|---|---|---|---|
| Volvic | about 7 °fH | about 6 °fH | very good, close to the target range |
| Acqua Panna | about 11 °fH | about 9 °fH | tastes good, somewhat more scale-forming |
| Evian | about 31 °fH | about 30 °fH | unsuitable, too hard |
| Highly mineralised waters (e.g. with a lot of calcium and sulphate) | often over 50 °fH | varies | unsuitable |
Values from manufacturer analyses or calculated from the label information. The composition may vary slightly between bottlings.
How to convert any label yourself:
- Total hardness in °fH = (calcium in mg/L × 2.5 + magnesium in mg/L × 4.12) ÷ 10
- Carbonate hardness in °fH = hydrogen carbonate (HCO₃) in mg/L ÷ 12.2
Example Evian: calcium 80 mg/L and magnesium 26 mg/L give (200 + 107) ÷ 10 = about 31 °fH.
Pros and cons of bottled water:
- Pros: consistent quality, no installation, very good results with the right water
- Cons: expensive in continuous use, lots of packaging and carrying, not practical for machines with a mains water connection or in hospitality
Water treatment: what is there and what is it worth?
| Method | How it works | Pros | Cons | Suitable for |
|---|---|---|---|---|
| Filter jug | ion exchanger and activated carbon reduce scale and off-flavours | cheap, simple | hardness varies over the cartridge's life, hygiene with long standing times | machines with a tank, at home |
| Whole-house softener | ion exchanger replaces calcium and magnesium with sodium | protects the whole house installation | water too high in sodium for coffee, tastes flat; not ideal for espresso | households in general, not as a coffee filter |
| Filter cartridge (e.g. BWT) | multi-stage: particle and activated carbon filter, ion exchanger, adjustable bypass blending | can be set precisely to the local hardness, protects against scale, improves taste | change the cartridge by volume or after 12 months at the latest | hospitality, machines with mains water, demanding home users |
| Reverse osmosis | a membrane removes almost all minerals and impurities | independent of the raw water, very consistent | expensive, waste water, too aggressive for the machine without remineralisation or bypass | very hard or contaminated water, specialty coffee |
| Remineralisation | targeted addition of minerals to osmosis or distilled water | precisely planned water recipes | effort, expertise needed | coffee enthusiasts, osmosis systems |
| Bypass blending | mix of filtered and unfiltered water | hits the target hardness exactly, part of many professional filter heads | must be set correctly, otherwise too hard or too soft | in combination with a cartridge or osmosis |
| Distilled water | water without minerals | no scale | tastes empty and sour, can attack metal, many machines do not detect the water level | not recommended |
Our assessment:
- For most portafilter machines with a mains water connection, a filter cartridge with adjustable bypass blending is the best solution. BWT offers several types: cartridges that add magnesium for hard water, special versions for when total hardness is much higher than carbonate hardness, and pure taste filters for soft water.
- Distilled water is a common mistake. Many machines measure the water level in the boiler by conductivity. Without minerals this measurement does not work, and over time the water attacks metal parts.
- Reverse osmosis is mainly worthwhile with very hard water in hospitality or when maximum consistency is required. Always with remineralisation or bypass blending.
How water tastes in the cup
The same beans, the same grinder, the same machine – and still the espresso can taste completely different. Often it is down to the water.
| Water | Taste in the espresso |
|---|---|
| Very hard, high carbonate hardness | flat, chalky, dull; acidity and fruit are lost, the crema often becomes patchy |
| Balanced (about 5–8 °fH, little carbonate hardness) | clear, sweet, with lively acidity and full body |
| Very soft or demineralised | sharp, sour, thin and empty |
| Chlorinated or with off-flavours | musty, "like a swimming pool" |
Why that is:
- Magnesium and calcium extract aroma compounds from the coffee. Without them, a lot of flavour stays in the bean.
- Carbonate hardness neutralises acidity. A little rounds the espresso off, too much wipes out the aromas.
- The ratio is decisive: two waters with the same total hardness can taste very different if their carbonate hardness differs.
A simple test: brew the same coffee once with your tap water and once with Volvic. The difference shows you how much your water matters.
Our recommendation in three steps
- Find out the hardness: look up or measure the total hardness and, if possible, the carbonate hardness of your tap water.
- Choose the right solution: with soft water a taste filter is often enough. From medium hard upwards you need a filter cartridge with bypass blending. With very hard water, reverse osmosis with remineralisation is also an option. At home with a tank machine, Volvic is a simple alternative.
- Change the filter on time: an exhausted filter no longer protects. Stick to the litre capacity and time interval stated by the manufacturer.
Frequently asked questions
Can I simply use tap water?
In regions with soft water, often yes. On the Central Plateau, in north-eastern Switzerland and in the Jura the water is usually too hard for espresso – without a filter the machine scales up quickly and the coffee tastes flat.
Isn't distilled water the gentlest for the machine?
No. Without minerals the coffee tastes empty, the water can attack metal parts, and many machines no longer detect the level in the boiler.
Which mineral water is best?
Soft waters such as Volvic are close to ideal. Acqua Panna tastes very good but is somewhat more scale-forming. Hard mineral waters such as Evian are unsuitable for espresso machines.
How often do I need to change the filter cartridge?
After the litre capacity the manufacturer states for your water hardness, but after twelve months at the latest.
Coffee beans: roast level and origin explained