Water hardness in Fond du Lac
19 gpg very hard
Tap water in Fond du Lac is very hard: 19 gpg (325 mg/L · 18.2 °dH · 32.5 °fH).
Source: Wisconsin DNR Drinking Water System portal (Fond Du Lac Waterworks) (2026) · data checked 2026-10-20
Range across supply zones: 290–370 mg/L.
Fond Du Lac Waterworks supplies the city from municipal groundwater wells. The area sits over Niagara dolomite and glacial deposits, both rich in carbonate, which gives very hard water at 325 mg/L CaCO₃ (290–370 mg/L). Heavy scale on heaters and fixtures.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 19 gpg |
|---|---|
| Utility | Fond Du Lac Waterworks |
How Fond du Lac compares
- Tap water in Fond du Lac is 110 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 182 of 1372 in the United States (1 = hardest); 87 % of these cities have softer water.
- In Wisconsin it is number 106 of 448 cities; the regional median is 14.3 gpg.
- Nearest city with clearly softer water: Waupun, 29 km away (4.8 gpg).
- Nearest city with clearly harder water: Campbellsport, 23 km away (25.5 gpg).
Ranking of the hardest and softest water in the United States →
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 Fond du Lac
| Brand | Setting for this water |
|---|---|
| Bosch | H05 |
| Miele | 18 °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 Fond du Lac water hard or soft?
It is very hard: 325 mg/L as CaCO₃ (19 gpg, 18.2 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Fond du Lac safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
How many grains per gallon is Fond du Lac water?
19 gpg, equal to 18.2 °dH, 32.5 °fH or 325 mg/L calcium carbonate.
What dishwasher salt setting should I use in Fond du Lac?
For 325 mg/L (18.2 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Fond du Lac?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: Wisconsin DNR Drinking Water System portal (Fond Du Lac Waterworks) (2026). Method: figure published by the water supplier. Wisconsin DNR Drinking Water System portal (Fond Du Lac Waterworks) · Outdated figure? Tell us