Water hardness in St. Paul
5.3 gpg moderately hard
Tap water in St. Paul is moderately hard: 5.3 gpg (90 mg/L · 5 °dH · 9 °fH).
Source: Saint Paul Regional Water Services, Monthly Water Quality (Mineral) Report, April 2025 (2025-04) · data checked 2026-10-23
Range across supply zones: 80–100 mg/L.
Saint Paul Regional Water Services takes its primary supply from the Mississippi River at Fridley, which flows through a chain of lakes north of the city before treatment, with groundwater wells as backup. Hardness is 90 mg/L CaCO₃ (80–100 mg/L). That is moderately hard, with some 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 | 5.3 gpg |
|---|---|
| Calcium (mg/L) | 21 |
| Magnesium (mg/L) | 9 |
| Utility | Saint Paul Regional Water Services |
How St. Paul compares
- Tap water in St. Paul is 42 % softer than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 1061 of 1372 in the United States (1 = hardest); 22 % of these cities have softer water.
- In Minnesota it is number 20 of 23 cities; the regional median is 17 gpg.
- Nearest city with clearly softer water: Colfax, 107 km away (1.2 gpg).
- Nearest city with clearly harder water: Eagan, 16 km away (19.1 gpg).
Ranking of the hardest and softest water in the United States →
What it means at home
- Visible kettle scale every few weeks; vinegar or citric acid is enough.
- Water heater and washing machine: some long-term scale; a scale inhibitor slows it.
- Dishwasher: medium salt setting.
- Softener optional; pays off mainly with a gas boiler or tankless heater.
How much salt will you use for softening?
Optional. A scale inhibitor or a small softener protects the heater; soap savings are modest.
Descale a coffee machine or kettle about every 3 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in St. Paul
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 5 °dH |
| AEG / Electrolux | 2 |
| Beko | 2nd |
| Hoover | S1 |
| LG | H1 |
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 St. Paul water hard or soft?
It is moderately hard: 90 mg/L as CaCO₃ (5.3 gpg, 5 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in St. Paul 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 St. Paul water?
5.3 gpg, equal to 5 °dH, 9 °fH or 90 mg/L calcium carbonate.
What dishwasher salt setting should I use in St. Paul?
For 90 mg/L (5 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in St. Paul?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: Saint Paul Regional Water Services, Monthly Water Quality (Mineral) Report, April 2025 (2025-04). Method: figure published by the water supplier. Saint Paul Regional Water Services, Monthly Water Quality (Mineral) Report, April 2025 · Outdated figure? Tell us