Water hardness in Aarau
30.4 °fH very hard
Tap water in Aarau is very hard: 30.4 °fH (304 mg/L · 17.8 gpg · 17 °dH).
Source: SVGW trinkwasser.ch (Eniwa Wasser AG supplier entry) (2025) · data checked 2026-11-14
The 304.3 mg/L CaCO₃ shown for Aarau is the 2025 entry for Eniwa Wasser AG on trinkwasser.ch. It covers a shared supply area (Aarau, Küttigen, Eppenberg-Wöschnau and Erlinsbach AG), not Aarau alone. The water is very hard. Expect visible limescale on taps and in kettles, and check the dishwasher salt setting.
In der Schweiz wird meist in °fH angegeben (1 °fH = 0,56 °dH).
Water data
| Total hardness | 30.4 °fH |
|---|---|
| Utility | Eniwa Wasser AG (supplier entry Aarau - Küttigen - Eppenberg-Wöschnau - Erlinsbach AG) |
How Aarau compares
- Tap water in Aarau is 14 % harder than the median of the 650 cities we track in Switzerland (26.7 °fH).
- By hardness it ranks 221 of 650 in Switzerland (1 = hardest); 66 % of these cities have softer water.
- In AG it is number 74 of 116 cities; the regional median is 32.3 °fH.
- Nearest city with clearly softer water: Unterentfelden, 3 km away (23.3 °fH).
- Nearest city with clearly harder water: Frick, 13 km away (41.1 °fH).
Ranking of the hardest and softest water in Switzerland →
What it means at home
- Severe scale: heater elements and washing-machine heaters fail early.
- Detergent use is very high; taps and screens coat within days.
- Dishwasher at maximum salt setting.
- An ion-exchange softener is practically essential; RO for drinking water.
How much salt will you use for softening?
Yes. At this hardness a softener pays for itself through appliance life and detergent.
Descale a coffee machine or kettle about every 1 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Aarau
| Brand | Setting for this water |
|---|---|
| Bosch | H05 |
| Miele | 17 °dH |
| AEG / Electrolux | 4 |
| Beko | 5th |
| Hoover | S3 |
| LG | H3 |
From each brand's manual for the model family named in the source; your model may differ, so check its manual. All brands and how to change the setting →
FAQ
Is Aarau water hard or soft?
It is very hard: 304 mg/L as CaCO₃ (17.8 gpg, 17 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Aarau safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. In der Schweiz wird meist in °fH angegeben (1 °fH = 0,56 °dH).
How many grains per gallon is Aarau water?
17.8 gpg, equal to 17 °dH, 30.4 °fH or 304 mg/L calcium carbonate.
What dishwasher salt setting should I use in Aarau?
For 304 mg/L (17 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Aarau?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: SVGW trinkwasser.ch (Eniwa Wasser AG supplier entry) (2025). Method: figure published by the water supplier. SVGW trinkwasser.ch (Eniwa Wasser AG supplier entry) · Outdated figure? Tell us