Water hardness in Tournai
36.8 °fH very hard
Tap water in Tournai is very hard: 36.8 °fH (368 mg/L · 21.5 gpg · 20.6 °dH).
Source: SPW, qualité de l'eau potable par zone de distribution, année civile 2025 (2025) · data checked 2026-10-19
SWDE supplies this area mostly from groundwater held in limestone and chalk, while part of Walloon supply comes from surface water; water that has passed through lime-rich rock is naturally hard. The reported 2025 figure is 368.0 mg/L CaCO₃ and no range is given for this supply area. 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 | 36.8 °fH |
|---|---|
| Utility | SWDE |
How Tournai compares
- Tap water in Tournai is 17 % harder than the median of the 1091 cities we track in Belgium (31.6 °fH).
- By hardness it ranks 322 of 1091 in Belgium (1 = hardest); 70 % of these cities have softer water.
- In Hainaut it is number 160 of 271 cities; the regional median is 38 °fH.
- Nearest city with clearly softer water: Vezon, 9 km away (26.1 °fH).
- Nearest city with clearly harder water: Hensies, 28 km away (47.2 °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 Tournai
| Brand | Setting for this water |
|---|---|
| Bosch | H05 |
| Miele | 21 °dH |
| AEG / Electrolux | 5 |
| Beko | 6th |
| 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 Tournai water hard or soft?
It is very hard: 368 mg/L as CaCO₃ (21.5 gpg, 20.6 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Tournai 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 Tournai water?
21.5 gpg, equal to 20.6 °dH, 36.8 °fH or 368 mg/L calcium carbonate.
What dishwasher salt setting should I use in Tournai?
For 368 mg/L (20.6 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Tournai?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: SPW, qualité de l'eau potable par zone de distribution, année civile 2025 (2025). Method: figure published by the water supplier. SPW, qualité de l'eau potable par zone de distribution, année civile 2025 · Outdated figure? Tell us