Cohasset Water Dept water quality
Cohasset, MA · serves 7,555 people (2,692 connections) · Surface water · Local government · EPA ID MA4065000
Data: U.S. EPA · How we read the data · How we check it
Summary
PFAS above the 2024 federal limits. Systems have until 2029 to meet the PFAS limits.
Is it an emergency? No: PFAS limits are about years of exposure, not a glass of water, and nothing in EPA's data calls for you to stop drinking the water today. If your utility ever issues a boil-water or do-not-drink notice, follow it.
- PFAS
- Above limitPFOA above the federal limit in EPA's 2023–2025 testing (PFOA 4.05 ppt vs a limit of 4 ppt, where ppt = parts per trillion).
- Lead
- Below action level2 ppb (parts per billion) at the 90th percentile: 9 in 10 homes sampled were at or below it. Action level 15 ppb, falling to 10 ppb in Nov 2027. Monitoring period ending Dec 2025. Your home's pipes can make yours higher.
- Violations
- Resolved5 health-based violations since 2016, most recently Jul 2026.
- Pregnant, or mixing baby formula with tap water? Babies drink more water for their size, so PFAS exposure matters more for them. Consider bottled water or a filter certified for PFAS for formula, and ask your doctor. Health effects.
- To lower your PFAS exposure now, a home filter certified for PFAS reduction works (reverse osmosis, or activated carbon certified to NSF/ANSI 53 or 58). Filters for these results.
- Built before 1986, or not sure what your service line is made of? Check your service line and test your tap. Utility data can't show your pipes.
- Tested your own tap? Compare your result with these numbers. Moving? Compare this system with another.
- Read Cohasset Water Dept's annual water quality report (Consumer Confidence Report). It lists every regulated contaminant tested and is usually on the utility's website or mailed with your bill, and you can also request it at (781) 383-0057. EPA: how to find it.
PFAS (“forever chemicals”)
EPA UCMR 5: 1 entry point tested Mar 2025 to Dec 2025. "Average" is the highest entry-point average (non-detects counted as zero), the way EPA compares UCMR 5 results to the limits. ppt = parts per trillion. These results do not determine compliance.
| Contaminant | Highest average |
|---|---|
| PFOA Above limit Limit 4 ppt | 4.05 ppt at the limit |
| PFOS One sample above limit Limit 4 ppt | 1.13 ppt 28% of the limit |
| PFHxS Not detected Limit 10 ppt | – |
| PFNA Not detected Limit 10 ppt | – |
| HFPO-DA (GenX) Not detected Limit 10 ppt | – |
| Hazard Index (a combined score for PFHxS, PFNA, GenX and PFBS, where above 1 is over the limit) Not detected Limit 1 | – |
| PFBS Not detected Guideline 2,000 ppt | – |
| PFBA Detected, below limit Guideline 6,000 ppt | 1.82 ppt |
| PFHxA Detected, below limit Guideline 3,000 ppt | 1 ppt |
| PFPeA Detected, no limit | 1.15 ppt |
For context: the PFOA average is higher than at 74% of the Massachusetts systems EPA tested.
29 PFAS tested, 5 detected at least once. "Not detected" means below EPA's reporting limit (about 2 to 20 ppt depending on the chemical), not proven zero. PFAS not listed were not detected. The limits for PFHxS, PFNA, GenX and the Hazard Index were proposed for rescission in May 2026. That proposal is not final. Systems have until 2029 to meet the limits.
Lithium
Not detected in 4 samples (reporting limit 9 ppb). About lithium.
Lead and copper
Latest 90th percentile: 2 ppb lead (Jan 2023 – Dec 2025). Below action level
Highest since 2016: 11 ppb (Dec 2019).
| Monitoring period | Lead (90th pct.) |
|---|---|
| Jan 2023 – Dec 2025 | 2 ppb |
| Jan 2020 – Dec 2022 | 2 ppb |
| Jan 2017 – Dec 2019 | 11 ppb |
Earlier results (9)
| Jan 2014 – Dec 2016 | 5 ppb |
| Jan 2013 – Dec 2013 | 13 ppb |
| Jan 2012 – Dec 2012 | 2 ppb |
| Jan 2011 – Dec 2011 | 4 ppb |
| Jul 2010 – Dec 2010 | 12 ppb |
| Jan 2010 – Jun 2010 | 5 ppb |
| Jul 2009 – Dec 2009 | 20 ppb |
| Jan 2009 – Jun 2009 | 20 ppb |
| Jul 2008 – Dec 2008 | 13 ppb |
Lead comes from pipes and fixtures, not the source water, so it varies home to home. The 90th percentile means 9 in 10 sampled homes were at or below it. More on lead.
Violations
| When | What happened |
|---|---|
| Jul 2026 | The running annual average for TTHM was above the legal limit. EPA record: TTHM · Maximum Contaminant Level Violation, Average (limit 0.080 mg/L) Addressed |
| Jul 2025 – Apr 2026 4 times | The running annual average for TTHM was above the legal limit. EPA record: TTHM · Maximum Contaminant Level Violation, Average (limit 0.080 mg/L) Archived |
Health-based violations mean a contaminant exceeded a limit or a required treatment step was missed. Monitoring and reporting violations mean required tests or reports were late or missing, so the water's quality during that time is unknown. The total includes every violation in EPA's records, most of them paperwork.
Where it serves
Cohasset
ZIP codes the system reported serving: 02025, 02043
Nearby utilities
- Scituate Water Division Scituate · 5 mi · PFAS above limit
- Norwell Water Department Norwell · 7 mi · PFAS above limit
- Weymouth Water Department Weymouth Town · 8 mi
- Hanover Water Dept Hanover · 10 mi · PFAS above limit
- Quincy Water Dept. (MWRA) Quincy · 11 mi
- Braintree Water and Sewer Dept. Braintree Town · 11 mi · PFAS above limit
Questions
Is Cohasset Water Dept water safe to drink?
Cohasset Water Dept had 5 health-based violations since 2016, all since resolved. EPA testing found PFAS above the 2024 federal limits, which systems must meet by 2029. Federal data can't tell you about your own pipes: lead comes from service lines and plumbing, so test your tap if your home was built before 1986. For the official word, read the utility's annual Consumer Confidence Report.
Does Cohasset Water Dept water have PFAS?
Yes. EPA's 2023–2025 testing of Cohasset Water Dept found 5 PFAS at least once. The highest entry-point averages were above the federal limit for PFOA: PFOA 4.05 ppt (limit 4 ppt for PFOA and PFOS, 10 ppt for the others).
What is the lead level in Cohasset Water Dept water?
The most recent 90th-percentile lead result for Cohasset Water Dept is 2 ppb, for the period ending Dec 2025. The federal action level is 15 ppb, falling to 10 ppb in November 2027. The 90th percentile means 9 in 10 homes sampled were at or below this number. Individual homes can be higher.
Check these numbers yourself
Every figure on this page comes from public EPA records. You don't have to take our word for it:
- EPA's own report for MA4065000: violations, enforcement and inspections, straight from EPA.
- EPA UCMR 5 data: the PFAS and lithium results (search the file for PWSID MA4065000).
- EPA SDWIS download: the lead results, population and violation records we use.
- The utility's annual water quality report (Consumer Confidence Report): ask Cohasset Water Dept at (781) 383-0057, or see EPA's guide to finding it.
Found something that doesn't match? Tell us and we'll check it against EPA's records. How we check our data.
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.