Thornton City of Water Quality (Colorado) – 2025 Report Results

We read 25 results from Thornton City of’s 2025 water quality report. No results over a legal limit; 6 above a health goal or guideline.

Serves about 226,465 people · Water system ID CO0101150 · Read the district’s 2025 report (opens in a new tab)

Open this district in the water lookupCompare with your own test results, see the district map and get matched filters.

Results from the 2025 report

Each number is copied from the district’s report and links to the page it’s printed on. Where the report lists several plants, wells or purchased water, the highest is shown.

Contaminant	Result	Health goal	Legal limit	What it means
Bromatehighest running annual average · range ND to 6 · Treatment plants · 2025 report, page 9	1.2 ppb	0.1 ppb	10 ppb	Above the health goal12x the health goal
Copper90th percentile of 52 homes tested, 0 over the action level · printed as 473 ppb · Customer taps (52 samples) · 2025 report, page 9	0.47 ppm	0.3 ppm	1.3 ppm (action level)	Above the health goal1.6x the health goal
Lead90th percentile of 52 homes tested, 0 over the action level · Customer taps (52 samples) · 2025 report, page 9	2.4 ppb	0.2 ppb	15 ppb (action level)	Above the health goal12x the health goal
PFOA (a PFAS)highest running annual average · range ND to 6.4 · Thornton plant · 2025 report, page 10	3.6 ppt	0.007 ppt	4 ppt from 2029	Above the health goal514x the health goal
PFOS (a PFAS)highest running annual average · range ND to 4.7 · Thornton plant · 2025 report, page 10	2.7 ppt	1 ppt	4 ppt from 2029	Above the health goal2.7x the health goal
Total dissolved solidshighest measured · range 195 to 679 · Treatment plants · 2025 report, page 10	679 ppm	—	500 ppm guideline	Above the guideline1.4x the guideline (taste, odor or stains; not a health limit)
Bariumhighest measured · range 0.05 to 0.05 · printed as 54 ppb · Treatment plants · 2025 report, page 9	0.05 ppm	2 ppm	2 ppm	Below the health goal
Chloraminehighest running annual average · range 0.8 to 3.9 · Distribution system · 2025 report, page 9	2.6 ppm	None set	4 ppm	Below the legal limit
Chloridehighest measured · range 47 to 173 · Treatment plants · 2025 report, page 10	173 ppm	—	250 ppm guideline	Within the guideline
Disinfection byproducts (HAA5)highest running annual average · range 2.6 to 16.4 · Distribution system · 2025 report, page 9	11.3 ppb	None set	60 ppb	Below the legal limit
Disinfection byproducts (TTHM)highest running annual average · range 19.6 to 61.1 · Distribution system · 2025 report, page 9	35.8 ppb	None set	80 ppb	Below the legal limit
Fluoridehighest measured · range 0.6 to 0.9 · Treatment plants · 2025 report, page 9	0.9 ppm	1 ppm	4 ppm	Below the health goal
Ironhighest measured · range ND to 0.06 · printed as 60 ppb · Treatment plants · 2025 report, page 10	0.06 ppm	—	0.3 ppm guideline	Within the guideline
Manganesehighest measured · range ND to 0.03 · printed as 34 ppb · Treatment plants · 2025 report, page 10	0.03 ppm	—	0.05 ppm guideline	Within the guideline
Nitrate (as N)highest measured · range 0.1 to 0.8 · Treatment plants · 2025 report, page 9	0.8 ppm	10 ppm	10 ppm	Below the health goal
Nitrite (as N)highest measured · range ND to 0.08 · Treatment plants · 2025 report, page 9	0.08 ppm	1 ppm	1 ppm	Below the health goal
PFHxS (a PFAS)highest measured · range ND to 0.5 · Treatment plants · 2025 report, page 10	0.5 ppt	None set	10 ppt from 2029	Below the legal limit
pHaverage · range 7.4 to 9 · Distribution system · 2025 report, page 10	8.1	—	—	Normal range
Seleniumhighest measured · range 0.8 to 1.7 · Treatment plants · 2025 report, page 9	1.7 ppb	30 ppb	50 ppb	Below the health goal
Sulfatehighest measured · range 70 to 187 · Treatment plants · 2025 report, page 10	187 ppm	—	250 ppm guideline	Within the guideline
Calciumhighest measured · range 50 to 73 · Treatment plants · 2025 report, page 10	73 ppm	None set	None	No health limit
Magnesiumhighest measured · range 12 to 18 · Treatment plants · 2025 report, page 10	18 ppm	None set	None	No health limit
Nickelsingle sample · Treatment plants · 2025 report, page 9	2 ppb	None set	None	No health limit
Potassiumhighest measured · range 4 to 10 · Treatment plants · 2025 report, page 10	10 ppm	None set	None	No health limit
Sodiumhighest measured · range 63 to 100 · Treatment plants · 2025 report, page 10	100 ppm	None set	None	No health limit

Utility results describe the whole system, measured where water enters the pipes, not your tap. Your home’s plumbing can add lead or copper. 1 number we weren’t sure about is held back until a person checks.

EPA testing for PFAS and lithium

EPA’s own nationwide testing (UCMR 5) found these in Thornton City of’s water between Feb 2023 and Nov 2023. These are EPA lab results, separate from the district’s report. Anything not listed was not detected.

PFOA7.1 pptFound in 2 of 7 samples · highest resultAbove the federal limit that takes effect in 2029 (4 ppt)
PFOS5 pptFound in 2 of 7 samples · highest resultAbove the federal limit that takes effect in 2029 (4 ppt)
PFHxS5.9 pptFound in 2 of 7 samples · highest resultNo federal limit in force for this one
PFBS8.1 pptFound in 7 of 7 samples · highest resultNo federal limit in force for this one
Lithium34 ppbFound in 7 of 7 samples · highest resultAbove EPA’s health reference level of 10 ppb (a guide, not a legal limit)

Source: EPA UCMR 5 occurrence data. The highest single result is shown; one high sample doesn’t mean every glass is that high.

What you can do

Nothing here is an emergency notice: if the district has a violation, it must tell customers directly. If you’d like to lower these at your tap, these are the treatments that remove them, and the catalog shows the models certified for each. Ranking is by certified removal; commissions never change the order.