Longmont, CO water hardness

Tap water hardness
20mg/L
1.2gpg
Soft

Reported by Longmont City of · September 2025

CO typical
97 mg/L
EPA health violations since 2016
0
Data
Utility report

Longmont water measures 20 mg/L (1.2 gpg) of hardness, soft by USGS standards. The number comes from Longmont City of, dated September 2025.

Longmont on the hardness scale, with nearby cities
060120180240300360+CO typical 97Loveland: 28 mg/LLoveland 28Louisville: 32 mg/LLouisville 32Erie: 33 mg/LErie 33Mead: 36 mg/LMead 36Berthoud: 36 mg/LBerthoud 36Boulder: 41 mg/LBoulder 41Broomfield: 46 mg/LBroomfield 46Johnstown: 59 mg/LJohnstown 59Lafayette: 91 mg/LLafayette 91Firestone: 415 mg/LFirestone 415Longmont 20mg/L as calcium carbonate060120180240300360+CO 97Erie: 33 mg/LErie 33Mead: 36 mg/LMead 36Berthoud: 36 mg/LBerthoud 36Boulder: 41 mg/LBoulder 41Lafayette: 91 mg/LLafayette 91Firestone: 415 mg/LFirestone 41520 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

At 20 mg/L, Longmont is 77 mg/L below the typical Colorado figure of 97. None of the 10 nearest cities we track has softer water. The range nearby runs from 28 mg/L in Loveland to 415 in Firestone.

What 20 mg/L means at home

Soap and shampoo lather with very little product. Kettles and showerheads stay mostly free of white crust.

Some people notice that soap feels slow to rinse off in soft water. That slippery feel is normal and harmless.

Hardness is not a health problem, and EPA sets no limit for it. It is a matter of scale and soap.

What to do about it

Nothing, as far as hardness goes. At 20 mg/L a softener would have almost nothing to remove.

Carbon filter

If the water tastes of chlorine, a pitcher or faucet carbon filter takes care of that. It does not change hardness.

EPA record for Longmont's water system

Longmont City of · PWSID CO0107485

No health-based violations since 2016

Serves about 104,178 people from surface water.

Health-based
0
Monitoring or reporting
2
Open now
0

Health-based means a contaminant above its legal limit or a missed treatment step. Monitoring and reporting violations are late or missing tests and notices. Source: EPA ECHO, 2026Q3 export, violations with periods starting 2016 or later. Full EPA record.

Questions

Is Longmont water hard?

No. It measures about 20 mg/L (1.2 grains per gallon), which the USGS classes as soft.

What is the water hardness in Longmont in grains per gallon?

About 1.2 gpg. One grain per gallon equals 17.1 mg/L, so 20 mg/L divided by 17.1 gives 1.2.

Has the Longmont water system had EPA violations?

EPA records show no health-based violations for Longmont City of since 2016. There were also 2 monitoring or reporting violations, which are about late or missing tests and notices.

Nearby cities

All 64 cities in Colorado

Hardness data: TapWaterData US Water Hardness (utility report, September 29, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.