Water hardness in Longmont
1.3 gpg soft
Tap water in Longmont is soft: 1.3 gpg (22 mg/L · 1.2 °dH · 2.2 °fH).
Source: City of Longmont 2025 Water Quality Report (2025) · data checked 2026-10-19
Range across supply zones: 19–25 mg/L.
The City of Longmont's 2025 water quality report gives an average total hardness of 21.7 mg/L (1.3 gpg), with a range of 19 to 25 mg/L. The report narrative puts it at 1 to 2 gpg. The table prints ppm without naming CaCO3, so we treat it as CaCO3 with some caution. This is very soft water, consistent with a mountain snowmelt supply. Scale is negligible.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 1.3 gpg |
|---|---|
| Utility | City of Longmont Water Department |
How Longmont compares
- Tap water in Longmont is 86 % softer than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 1328 of 1372 in the United States (1 = hardest); 3 % of these cities have softer water.
- In Colorado it is number 11 of 11 cities; the regional median is 6.1 gpg.
- Nearest city with clearly harder water: Boulder, 22 km away (2.5 gpg).
Ranking of the hardest and softest water in the United States →
What it means at home
- Little or no limescale in kettles, water heaters or washing machines.
- Soap lathers easily; water does not dry skin or hair.
- Dishwasher: salt setting at minimum or off.
- No softener needed; a jug filter only changes taste.
How much salt will you use for softening?
No. Water this soft does not need softening.
Descale a coffee machine or kettle about every 6 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Longmont
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 1 °dH |
| AEG / Electrolux | 1 |
| Beko | 1st |
| Hoover | S0 |
| LG | H0 |
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 Longmont water hard or soft?
It is soft: 22 mg/L as CaCO₃ (1.3 gpg, 1.2 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Longmont 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 Longmont water?
1.3 gpg, equal to 1.2 °dH, 2.2 °fH or 22 mg/L calcium carbonate.
What dishwasher salt setting should I use in Longmont?
For 22 mg/L (1.2 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Longmont?
No. With soft water a softener adds nothing.
Source
Source: City of Longmont 2025 Water Quality Report (2025). Method: figure published by the water supplier. City of Longmont 2025 Water Quality Report · Outdated figure? Tell us