Water hardness in Des Plaines
7.9 gpg hard
Tap water in Des Plaines is hard: 7.9 gpg (136 mg/L · 7.6 °dH · 13.6 °fH).
Source: City of Chicago DWM, Comprehensive Chemical Analysis 2025 (quarterly, plant outlets) (2025) · data checked 2026-10-23
Range across supply zones: 120–149 mg/L.
2 supply zones — hardness varies by neighbourhood; the figure above is the median.
Hardness by district / supply zone
| gpg | mg/L | ||
|---|---|---|---|
| City of Chicago supply (Lake Michigan, plant not stated) | 7.9 | 135 | hard |
| Northwest Water Commission supply (Evanston-treated Lake Michigan water) | 8 | 137 | hard |
Des Plaines buys Lake Michigan water from the City of Chicago and from the Northwest Water Commission, so the 2 sources differ slightly: 135.8 mg/L CaCO₃, from 120 to 149 mg/L. Lake water carries carbonate from limestone and dolomite in its basin. Hard water, with scale on kettles and heaters.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 7.9 gpg |
|---|---|
| Utility | City of Des Plaines Public Works (buys Lake Michigan water from City of Chicago and Northwest Water Commission) |
How Des Plaines compares
- Tap water in Des Plaines is 12 % softer than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 799 of 1372 in the United States (1 = hardest); 42 % of these cities have softer water.
- In Illinois it is number 9 of 14 cities; the regional median is 8 gpg.
- Nearest city with clearly softer water: Bloomfield, 69 km away (1 gpg).
- Nearest city with clearly harder water: Bristol, 56 km away (14 gpg).
Ranking of the hardest and softest water in the United States →
What it means at home
- Fast scale on taps, shower screens and kettle; white spots on glassware.
- Water heater: efficiency loss and element failures within years if unprotected.
- Dry skin and dull hair after showering are common.
- Softener recommended; jug or reverse osmosis for drinking.
How much salt will you use for softening?
Recommended, especially with a heater or boiler: scale cuts efficiency and shortens its life.
Descale a coffee machine or kettle about every 2 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Des Plaines
| Brand | Setting for this water |
|---|---|
| Bosch | H01 |
| Miele | 8 °dH |
| AEG / Electrolux | 2 |
| Beko | 2nd |
| Hoover | S1 |
| 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 Des Plaines water hard or soft?
It is hard: 136 mg/L as CaCO₃ (7.9 gpg, 7.6 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Des Plaines 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 Des Plaines water?
7.9 gpg, equal to 7.6 °dH, 13.6 °fH or 136 mg/L calcium carbonate.
What dishwasher salt setting should I use in Des Plaines?
For 136 mg/L (7.6 °dH) check your manufacturer's table: level 4–5.
Do I need a water softener in Des Plaines?
Recommended if you have a water heater, boiler or tankless unit: it saves repairs and detergent.
Source
Source: City of Chicago DWM, Comprehensive Chemical Analysis 2025 (quarterly, plant outlets) (2025). Method: figure published by the water supplier. City of Chicago DWM, Comprehensive Chemical Analysis 2025 (quarterly, plant outlets) · Outdated figure? Tell us