Water hardness in Zemst
18.4 °fH very hard
Tap water in Zemst is very hard: 18.4 °fH (184 mg/L · 10.8 gpg · 10.3 °dH).
Source: VMM, Kwaliteit van het drinkwater per leveringsgebied 2024, bijlage 2 (mediane concentratie) (2024) · data checked 2026-10-19
Range across supply zones: 174–363 mg/L.
De Watergroep supplies this part of Flanders with a mix of groundwater and canal-fed surface water, so hardness sits between the soft sandy Campine and the hard chalk areas. The 2024 figure is 184.4 mg/L CaCO₃, within a reported range of 173.9 to 363.4 mg/L, so the exact value depends on your street. This is very hard water: expect heavy limescale on taps, glass and heating elements, and higher detergent and descaling needs.
Belgian suppliers report hardness in °f (French degrees); 1 °f = 10 mg/L CaCO₃.
Water data
| Total hardness | 18.4 °fH |
|---|---|
| Utility | De Watergroep |
How Zemst compares
- Tap water in Zemst is 42 % softer than the median of the 1091 cities we track in Belgium (31.6 °fH).
- By hardness it ranks 798 of 1091 in Belgium (1 = hardest); 27 % of these cities have softer water.
- In Vlaams-Brabant it is number 39 of 59 cities; the regional median is 26.6 °fH.
- Nearest city with clearly softer water: Diest, 41 km away (14 °fH).
- Nearest city with clearly harder water: Vilvoorde, 7 km away (36.3 °fH).
Ranking of the hardest and softest water in Belgium →
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 Zemst
| Brand | Setting for this water |
|---|---|
| Bosch | H02 |
| Miele | 10 °dH |
| AEG / Electrolux | 2 |
| Beko | 3rd |
| Hoover | S2 |
| LG | H2 |
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 Zemst water hard or soft?
It is very hard: 184 mg/L as CaCO₃ (10.8 gpg, 10.3 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Zemst safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. Belgian suppliers report hardness in °f (French degrees); 1 °f = 10 mg/L CaCO₃.
How many grains per gallon is Zemst water?
10.8 gpg, equal to 10.3 °dH, 18.4 °fH or 184 mg/L calcium carbonate.
What dishwasher salt setting should I use in Zemst?
For 184 mg/L (10.3 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Zemst?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: VMM, Kwaliteit van het drinkwater per leveringsgebied 2024, bijlage 2 (mediane concentratie) (2024). Method: figure published by the water supplier. VMM, Kwaliteit van het drinkwater per leveringsgebied 2024, bijlage 2 (mediane concentratie) · Outdated figure? Tell us