Tap Water Quality Report
Tap water quality in DENNIS, Massachusetts
Tap water in DENNIS, Massachusetts receives a grade of C (71/100) from TapWaterSafety.org. It's served by DENNIS WATER DISTRICT. The most significant water quality concerns are: PFAS contamination; Perfluorohexane sulfonate (PFHXS) significantly above health guideline; Haloacetic acids (HAA9) significantly above health guideline; Total trihalomethanes (TTHMs) significantly above health guideline. Data sources: EPA SDWIS, EPA ECHO, EWG Tap Water Database.
What's in DENNIS's tap water
Top water quality concerns identified by the EPA and Environmental Working Group across the utility serving DENNIS.
PFAS contamination
Severe concernPerfluorooctanoic acid (PFOA), Perfluorooctane sulfonate (PFOS) detected. PFAS are persistent chemicals linked to cancer and immune effects with no known safe exposure threshold.
Perfluorohexane sulfonate (PFHXS) significantly above health guideline
Moderate concernPerfluorohexane sulfonate (PFHXS) detected at 0.151 ppt, 151x above the EWG health guideline of 0.001 ppt.
Haloacetic acids (HAA9) significantly above health guideline
Moderate concernHaloacetic acids (HAA9) detected at 3.8 ppb, 63x above the EWG health guideline of 0.06 ppb.
Total trihalomethanes (TTHMs) significantly above health guideline
Moderate concernTotal trihalomethanes (TTHMs) detected at 8.61 ppb, 57x above the EWG health guideline of 0.15 ppb.
EPA compliance record
Official U.S. EPA records for DENNIS WATER DISTRICT (system ID MA4075000) for the last 3 years. Checked 2026-10-07.
Source: U.S. EPA Enforcement and Compliance History Online (ECHO), from the Safe Drinking Water Information System. See EPA's full report.
Recommended filters for DENNIS
Filters matched to the specific contaminants in DENNIS's water supply.
Filter certified for PFOA/PFOS (NSF/ANSI 53 or 58)
$180-$750Reverse osmosis and some carbon block filters reduce PFAS. Look for certification to NSF/ANSI 53 or 58 for PFOA/PFOS.
Carbon filter certified for VOCs (NSF/ANSI 53)
$180-$599Activated carbon is effective for disinfection byproducts. Look for NSF/ANSI 53 VOC reduction.
Disclosure: TapWaterSafety earns a commission from purchases made through these links. This does not influence our scoring methodology or filter selection.
All contaminants detected in DENNIS's tap water
Every contaminant identified, compared side-by-side against US EPA legal limits, the EU Drinking Water Directive (2020/2184), WHO Guidelines, and California's Public Health Goal. Why we show multiple standards →
| Contaminant | Detected | EWG US health-based |
EPA US legal |
EU DWD Europe |
WHO global |
CA PHG strictest US |
Tested sample year |
Status |
|---|---|---|---|---|---|---|---|---|
| Perfluorohexane sulfonate (PFHXS) PFAS |
0.151 ppt | 0.001 | 10.0 | — | — | — | — | 151× over |
| Haloacetic acids (HAA9) Disinfection byproduct |
3.8 ppb | 0.06 | — | — | — | — | — | 63× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
8.61 ppb | 0.15 | 80.0 | 100 | — | — | — | 57× over |
| Dibromoacetic acid Disinfection byproduct |
0.843 ppb | 0.03 | — | — | — | — | — | 28× over |
| Bromodichloromethane Disinfection byproduct |
0.753 ppb | 0.06 | — | — | — | — | — | 13× over |
| Dibromochloromethane Disinfection byproduct |
1.13 ppb | 0.1 | — | — | — | — | — | 11× over |
| Haloacetic acids (HAA5) Disinfection byproduct |
1.06 ppb | 0.1 | 60.0 | 60 | — | — | — | 11× over |
| Nitrate Inorganic |
1.06 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 7.6× over |
| Radium, combined (-226 and -228) Radiological |
0.31 pCi/L | 0.05 | 5.0 | — | — | — | — | 6.3× over |
| Chloroform Disinfection byproduct |
2.1 ppb | 0.4 | — | — | — | — | — | 5.3× over |
| Chromium (hexavalent) Heavy metal |
0.0954 ppb | 0.02 | — | — | — | — | — | 4.8× over |
| Perfluorooctanoic acid (PFOA) PFAS |
0.357 ppt | 0.09 | 4.0 | 100 | 100 | 0.007 | — | 4.0× over |
| Bromoform Disinfection byproduct |
0.639 ppb | 0.5 | — | — | — | — | — | 1.3× over |
| Bromochloromethane Other |
0.0705 ppb | 0.06 | — | — | — | — | — | 1.2× over |
| Perfluorooctane sulfonate (PFOS) PFAS |
0.31 ppt | 0.3 | 4.0 | 100 | 100 | 1 | — | 1.0× over |
| Dichloroacetic acid Disinfection byproduct |
0.106 ppb | 0.2 | — | — | — | — | — | Below guideline |
| Chlorate Disinfection byproduct |
50.3 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Manganese Heavy metal |
13.7 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Barium Heavy metal |
21.2 ppb | 700.0 | 2000.0 | — | 1300 | 2000 | — | Below guideline |
| Monochloroacetic acid Disinfection byproduct |
0.114 ppb | 53.0 | — | — | — | — | — | Below guideline |
| Vanadium Other |
0.0104 ppb | 21.0 | — | — | — | — | — | Below guideline |
| Perfluorohexanoic Acid (PFHxA) PFAS |
0.396 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Perfluoropentanoic Acid (PFPeA) PFAS |
0.283 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Perfluoroheptanoic acid (PFHPA) PFAS |
0.122 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Perfluorobutane sulfonate (PFBS) PFAS |
0.179 ppt | 2000.0 | — | — | — | — | — | Below guideline |
| Strontium Radiological |
0.0379 ppb | 1500.0 | — | — | — | — | — | Below guideline |
All values in the unit of the detected level. Red cells indicate the detected level exceeds that standard. Some contaminants have limits in some jurisdictions but not others (shown as —). The "Tested" column shows the year each contaminant sample was collected.
Sources: US EPA, EU Drinking Water Directive 2020/2184, WHO Guidelines, California OEHHA PHGs, EWG Tap Water Database.
Treatment plant contact info
For service issues, water quality concerns, or to request a Consumer Confidence Report from DENNIS WATER DISTRICT.