01The verdict: is Marlborough water safe?
Marlborough's tap water meets most EPA standards but has areas that warrant attention. With a grade of A- (86.7/100), some contaminant levels or compliance issues suggest that residents may benefit from additional filtration. The city's 2 water systems serve approximately 850 residents using groundwater (wells).
Copper is over its legal limit
Measured at 2.52 mg/L against the EPA Action Level of 1.3 mg/L. The ledger below shows how far over — and which filter removes it.
See the measurement ↓Monitoring is on schedule
The system is meeting its EPA monitoring and reporting requirements — testing is happening when it should.
See the score ↓2 violations in the last five years
Recent compliance history is the best predictor of future problems — the year-by-year record is below.
See the record ↓Marlborough's drinking water received a grade of A- (86.7 out of 100), indicating good water quality. The city's 2 water systems serve approximately 850 residents using groundwater.
Lead data is not currently available for this system. This system has not yet been tested for PFAS under the EPA UCMR 5 program. The system has 75 violations on record, including 4 health-based violations. 2 remain unresolved.
Marlborough ranks #15 out of 98 cities in New Hampshire for water quality, placing it above average in the state. Marlborough 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, Marlborough may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
02What's in Marlborough's water
Every contaminant flagged in Marlborough, 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.
Over Limit — EPA Action Level: 1.3 mg/L
Exceeds the EPA action level. Copper leaches from household plumbing — flush taps for 30 seconds before drinking, and consider a certified filter.Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Copper (90th percentile) CopperInorganic A metal that enters drinking water mainly through corrosion of copper plumbing. Small amounts are essential for health, but excess levels are harmful. Health EffectsGastrointestinal distress (nausea, vomiting, diarrhea) at short-term high levels; liver and kidney damage from long-term exposure. EPA Limit1.3 mg/L action level Common SourcesCorrosion of copper household plumbing, erosion of natural deposits. | 2.52 | 1.3 | mg/L | Inorganic | Over Limit |
Cities ranked by 90th-percentile lead PF PFAS in New Hampshire
Cities ranked by compounds detected Cu Copper in New Hampshire
Cities ranked by 90th-percentile copper
03Marlborough'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 75 violations on record, including 4 health-based violations. 2 remain unresolved.
9 of the last ten years were clean. The numbered years had EPA violations — red when any were health-based, amber when they were paperwork or missed-testing issues.
1.5mg/L(1993)
One sampling round on record — 118% of the 1.3mg/L EPA action level. Sampled at higher-risk homes (90th percentile).
04Where Marlborough's water comes from
Marlborough'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.
2 systems
2 water systems, operated under local government ownership.
850 people
Residents served across Marlborough'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 850 people through 2 water systems.
| System name | PWSID | Population | Source |
|---|---|---|---|
| MARLBOROUGH WATER WORKS | NH1481010 | 750 | Groundwater |
| MARLBOROUGH ESTATES | NH1482010 | 100 | Groundwater |
Water bodies near Marlborough
These water bodies shape the regional watershed and can indirectly affect groundwater quality.
05Pressure on Marlborough'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
10 federal disaster declarations on record for Cheshire County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
Superfund proximity
1 National Priorities List site within 10 miles. Proximity does not necessarily indicate tap-water contamination — the connection depends on hydrology and treatment.
Drought
Cheshire 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 Marlborough compares
Scores for nearby New Hampshire cities on one line, with the average marked.
dashed line = New Hampshire average (66/100)
Marlborough scores 86.7/100 — above the New Hampshire average of 66/100. It outscores 8 of 10 nearby cities. Full New Hampshire rankings →
50.9 / 100ANashua, NH
88.7 / 100DConcord, NH
51.3 / 100BPortsmouth, NH
80.7 / 100AKeene, NH
89.2 / 100BDover, NH
84 / 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 Marlborough's water — not generic advice.
Filter drinking & cooking water
Basic carbon filter for extra protection. Copper exceeds the EPA action level of 1.3 mg/L
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 Marlborough 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 Marlborough, NH tap water safe to drink?
Marlborough's water quality earned a grade of A- (86.7/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #15 out of 98 cities tested in New Hampshire.
What contaminants are in Marlborough's water?
75 violations are on record.
How is Marlborough'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 Marlborough?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Marlborough's water come from?
Marlborough's water is sourced from Groundwater. The city has 2 water systems serving approximately 850 residents.
What health violations has Marlborough's water system had?
Marlborough has 4 health-based violations on record. The most recent violation was recorded in July 2025. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 2 violations remain unresolved.
Is Marlborough's groundwater at risk of contamination?
Marlborough 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 75 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 Marlborough's water compare to other cities?
Marlborough ranks #15 out of 98 cities in New Hampshire (better than 85% of state cities) and #4520 out of 15382 cities nationally (71th percentile). The grade of A- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.