Water hardness in Centennial
6.7 gpg moderately hard
Tap water in Centennial is moderately hard: 6.7 gpg (115 mg/L · 6.4 °dH · 11.5 °fH).
Source: Centennial Water and Sanitation District 2024 Water Quality Report (2024) · data checked 2026-10-19
Range across supply zones: 68–150 mg/L.
Centennial Water and Sanitation District's 2024 report gives total hardness as CaCO3 of 115 mg/L (6.7 gpg) from daily sampling, with values from 68 to 150 mg/L. That is moderately hard water. The figure is for the district's service area, and we did not verify that it matches the city boundary. A scale inhibitor is often enough for the water heater.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 6.7 gpg |
|---|
How Centennial compares
- Tap water in Centennial is 26 % softer than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 930 of 1372 in the United States (1 = hardest); 32 % of these cities have softer water.
- In Colorado it is number 4 of 11 cities; the regional median is 6.1 gpg.
- Nearest city with clearly softer water: Commerce City, 33 km away (5.2 gpg).
- Nearest city with clearly harder water: Pueblo, 150 km away (10.5 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 Centennial
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 6 °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 Centennial water hard or soft?
It is moderately hard: 115 mg/L as CaCO₃ (6.7 gpg, 6.4 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Centennial 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 Centennial water?
6.7 gpg, equal to 6.4 °dH, 11.5 °fH or 115 mg/L calcium carbonate.
What dishwasher salt setting should I use in Centennial?
For 115 mg/L (6.4 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Centennial?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: Centennial Water and Sanitation District 2024 Water Quality Report (2024). Method: figure published by the water supplier. Centennial Water and Sanitation District 2024 Water Quality Report · Outdated figure? Tell us