01The verdict: is Mahnomen water safe?
Mahnomen's tap water meets most EPA standards but has areas that warrant attention. With a grade of A (91.6/100), some contaminant levels or compliance issues suggest that residents may benefit from additional filtration. The city's 1 water system serves approximately 1,210 residents using groundwater (wells).
1 unresolved violation on record
EPA records show an open compliance item for this system. Most are administrative, but unresolved items are worth watching.
See what was cited ↓Lead is well under the limit
90th-percentile lead is 0.0 ppb — beneath the 15 ppb federal action level and under the 5 ppb watch threshold.
See the trend ↓A flood-prone service area
9 federal disaster declarations on record. After severe weather, watch for boil-water advisories.
See the risk factors ↓Mahnomen's drinking water received a grade of A (91.6 out of 100), indicating excellent water quality. The city's 1 water system serves approximately 1,210 residents using groundwater.
Lead levels were measured at 0.0 ppb (90th percentile), well within EPA limits. This system has not yet been tested for PFAS under the EPA UCMR 5 program. The system has 3 violations on record, including 0 health-based violations. 1 remains unresolved.
Mahnomen ranks #160 out of 466 cities in Minnesota for water quality, placing it mid-range in the state. Mahnomen relies on groundwater, which is generally less vulnerable to surface contamination but can be affected by naturally occurring minerals like arsenic and nitrate, as well as agricultural and industrial runoff. As a small community water system, Mahnomen may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
02What's in Mahnomen's water
Every contaminant flagged in Mahnomen, on one shared scale: distance to its own legal limit. The red line is the limit — anything past it is out of compliance, and the closer a bar gets, the less headroom the system has.
Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Lead (90th percentile) LeadHeavy Metal A toxic heavy metal that can leach into drinking water from older pipes, solder, and fixtures. No amount of lead in water is considered safe. Health EffectsBrain and nervous system damage in children, kidney damage, high blood pressure, and reproductive problems in adults. EPA Limit15 ppb action level Common SourcesCorrosion of lead pipes, lead solder, brass faucets, and household plumbing. | 0.0 | 15 | ppb | Inorganic | Safe |
Cities ranked by 90th-percentile lead PF PFAS in Minnesota
Cities ranked by compounds detected Cu Copper in Minnesota
Cities ranked by 90th-percentile copper
03Mahnomen's ten-year track record
Each box is one year. A green check means no EPA violations; a numbered badge counts that year's violations — red if any were health-based, amber if they were monitoring or paperwork issues. The system has 3 violations on record, including 0 health-based violations. 1 remains unresolved.
All ten of the last ten years were clean — no EPA violations recorded for Mahnomen.
0ppb(2023)
One sampling round on record — 0% of the 15ppb EPA action level. Sampled at higher-risk homes (90th percentile).
04Where Mahnomen's water comes from
Mahnomen's drinking water is drawn from underground aquifers through wells.
Groundwater
Underground aquifers reached by wells — naturally filtered, but can carry minerals like arsenic and nitrate.
Local treatment
Groundwater generally needs less treatment — typically disinfection and, where needed, mineral removal.
1 system
1 water system, operated under local government ownership.
1,210 people
Residents served across Mahnomen's service area.
Groundwater is naturally filtered through rock and soil layers, generally requiring less treatment than surface water. However, it can contain naturally occurring contaminants like arsenic, radon, and minerals. Agricultural activity, septic systems, and industrial operations near well fields can introduce nitrates, pesticides, and volatile organic compounds. The system is operated by local government ownership and serves approximately 1,210 people through 1 water system.
| System name | PWSID | Population | Source |
|---|---|---|---|
| Mahnomen | MN1440002 | 1,210 | Groundwater |
05Pressure on Mahnomen's watershed
Outside forces that shape what reaches the treatment plant. None of these is a verdict on the tap by itself — but each adds pressure worth knowing about.
Flood & storm history
9 federal disaster declarations on record for Mahnomen County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
Drought
Mahnomen County is in D1 (moderate drought) per the U.S. Drought Monitor (week of Jul 2026). Drought can raise disinfection-byproduct levels and taste/odor issues as utilities draw from lower reservoirs.
06How Mahnomen compares
Scores for nearby Minnesota cities on one line, with the average marked.
dashed line = Minnesota average (82/100)
Mahnomen scores 91.6/100 — above the Minnesota average of 82/100. It outscores 9 of 10 nearby cities. Full Minnesota rankings →
72.8 / 100BSt. Paul, MN
73.3 / 100CRochester, MN
69.7 / 100ABloomington, MN
93.6 / 100BBrooklyn Park, MN
81.5 / 100ADuluth, MN
88.6 / 100
Compare all cities in the county — grades, violations, and contaminant data side by side.→
07What to do at home
Steps matched to what testing actually found in Mahnomen's water — not generic advice.
A basic carbon filter still helps
Mahnomen's water meets federal standards, but a simple carbon filter improves taste and adds a margin of safety against short-term issues.
Compare tested filters →Read your utility's annual report
Every utility must publish a yearly Consumer Confidence Report with its own testing results. It pairs well with the independent data on this page.
How to read a CCR →Watch for Mahnomen alerts
This area has a history of flood declarations — after severe weather, watch for boil-water advisories from the utility, and check the live alerts on this page.
All water alerts →Frequently asked questions
Is Mahnomen, MN tap water safe to drink?
Mahnomen's water quality earned a grade of A (91.6/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #160 out of 466 cities tested in Minnesota.
What contaminants are in Mahnomen's water?
Lead was measured at 0.0 ppb (90th percentile). 3 violations are on record.
How is Mahnomen's water quality grade calculated?
The grade is based on four factors: violation history (40%), lead and copper levels (25%), PFAS contamination (25%), and regulatory compliance (10%). The score is also adjusted based on how complete the available data is. See our methodology page for full details.
Do I need a water filter in Mahnomen?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Mahnomen's water come from?
Mahnomen's water is sourced from Groundwater. The city has 1 water system serving approximately 1,210 residents.
Is Mahnomen's groundwater at risk of contamination?
Mahnomen uses groundwater, which can be affected by naturally occurring contaminants like arsenic, radon, and nitrate, as well as agricultural runoff and industrial activity. The system has 3 violations on record that may relate to groundwater quality. Groundwater systems are generally less susceptible to surface contamination but should be monitored for emerging contaminants like PFAS.
How does Mahnomen's water compare to other cities?
Mahnomen ranks #160 out of 466 cities in Minnesota (better than 66% of state cities) and #1596 out of 15382 cities nationally (90th percentile). The grade of A reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Mahnomen's small water system affect quality?
Mahnomen's system serves approximately 1,210 residents. Small community water systems (under 3,300 people) may have fewer financial resources for infrastructure upgrades and advanced treatment technologies. However, they are held to the same EPA drinking water standards as larger systems. This system has 3 violations on record.