Is Denver tap water safe to drink?
In the latest results, every contaminant we list with a single federal limit was below that limit or action level. Lead was 3.6 ppb at the 90th percentile, below the 15 ppb action level. EPA’s goal for lead is zero. Lithium was found above EPA’s health reference level (10 ppb), a screening value that is not an enforceable limit. EPA lists no health-based violations in the last 10 years (35 monitoring, reporting or notice records). See how US tap water compares nationally.
What’s in Denver tap water
Latest results from Denver Water’s 2025 report and EPA records. One row per contaminant, with the type of limit in the limit column.
| Contaminant | Result | Limit | Sampled | Source |
|---|---|---|---|---|
| LeadComes mostly from home plumbing, not from the source water. | 3.6 ppb 90th percentile reported to EPA; previous round (Jul – Dec 2025): 3.1 ppb | 15 ppbAction level · goal 0Drops to 10 ppb on Nov 1, 2027 (Lead and Copper Rule Improvements). | Jan – Jun 2026 | EPA SDWIS record, CO0116001 |
| PFOA and PFOS (PFAS)Two “forever chemicals” with a federal limit. | Not detected 15 samples at 4 entry points; none at or above the reporting level (4 ppt) | 4.0 ppt eachLegal limit (MCL) · goal 0Utilities must comply from 2029; EPA proposed 2031 in May 2026. | Mar 2023 – Apr 2025 | EPA UCMR 5 final occurrence data (Aug 2026 release) |
| Total trihalomethanesByproducts of disinfection. | 35.5 ppb Highest locational running annual average; range 8.8–41.1 | 80 ppbLegal limit (MCL) | 2025 | Denver Water 2026 Water Quality Report (2025 data) |
| Haloacetic acids (HAA5)Byproducts of disinfection. | 19.5 ppb Highest locational running annual average; range 7.2–26.7 | 60 ppbLegal limit (MCL) | 2025 | Denver Water 2026 Water Quality Report (2025 data) |
| LithiumUnregulated; EPA is collecting national data. | Up to 10.8 ppb Found in 5 of 15 samples at 4 entry points; range 9–10.8 | 10 ppbEPA health reference levelA health reference level is a screening value, not an enforceable limit. | Mar 2023 – Apr 2025 | EPA UCMR 5 final occurrence data (Aug 2026 release) |
ppb = parts per billion (µg/L), ppt = parts per trillion (ng/L). The bar shows the result against the limit (black line). Limits: EPA drinking water regulations, PFAS rule, Lead and Copper Rule Improvements. “Not detected” means below the lab’s reporting level, not zero.
EPA violations
EPA’s SDWIS database lists 128 violation records for Denver Water since 2014, none of them health-based. 31 have no return-to-compliance date on EPA’s record.
Not listed: 93 older monitoring, reporting or notice records (2014), none health-based.
Shown: health-based violations and everything from the last 10 years. Source: EPA SDWIS record, CO0116001, retrieved Oct 13, 2026.
How hard is Denver water?
The utility’s figures cover the whole system. To test the hardness at your tap, strips or a drop kit take minutes.
Classes: USGS (0–60 mg/L soft, 61–120 moderately hard, 121–180 hard, above 180 very hard). 1 gpg = 17.1 mg/L as calcium carbonate. Source: Denver Water 2026 Water Quality Report (2025 data).
What to do with these numbers
Only what the data above points to.
Lead comes from home plumbing
EPA’s goal for lead is zero. Older faucets, lead solder and lead service lines can add lead at your tap. A filter certified to NSF/ANSI 53 for lead reduces it.
Certified to reduce lead. Lead is not necessarily in your water.
All filters compared →Test your own water
Denver Water’s numbers come from its own sampling sites. A certified lab test of your faucet shows lead and copper from your plumbing. How to test your own tap for lead, starting with your water utility.
All water tests compared →