Water Quality Report · Updated May 12, 2026
DENNIS WATER DISTRICT
DENNIS WATER DISTRICT delivers tap water graded D (56/100) by TapWaterSafety.org. The utility serves approximately 65,000 residents in DENNIS, Massachusetts using groundwater. 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. For questions, the utility can be reached at 5083983351.
Is DENNIS tap water safe to drink?
DENNIS WATER DISTRICT delivers tap water that earns a grade of D (56/100) from TapWaterSafety.org — a below-average rating, with multiple concerns including pfas contamination.
The utility serves 65,000 residents in DENNIS, drawing from groundwater.
Public testing data identifies 15 contaminants in this water above EWG's health-based guidelines, including: Perfluorohexane sulfonate (PFHXS), Haloacetic acids (HAA9), Total trihalomethanes (TTHMs), Dibromoacetic acid, Bromodichloromethane, Dibromochloromethane, Haloacetic acids (HAA5), Nitrate, Radium, combined (-226 and -228), Chloroform, Chromium (hexavalent), Perfluorooctanoic acid (PFOA), Bromoform, Bromochloromethane, Perfluorooctane sulfonate (PFOS). For most residents, a properly certified home filter at the kitchen tap is the most cost-effective way to reduce exposure to whatever's in your water. See our filter recommendations below, matched specifically to this utility's contaminant profile.
Quick actions for DENNIS residents
Top concerns in this water
Based on the most recent EPA and EWG data, these are the most significant water quality issues for DENNIS WATER DISTRICT.
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.
Contact DENNIS WATER DISTRICT
Reach the utility directly for service issues, water quality concerns, or to request your Consumer Confidence Report.
General Contact
Treatment Plant
Recommended water filters for DENNIS
Filters matched to the specific contaminants in this water supply.
Reverse Osmosis or NSF P473 certified carbon
$80-$750Activated carbon and RO are the only technologies proven to remove PFAS at certified levels.
Carbon block (NSF/ANSI 42 + 53)
$40-$750Activated carbon is highly effective for disinfection byproducts like TTHM and HAA5.
Disclosure: TapWaterSafety earns a commission from purchases made through these links. This does not influence our scoring methodology or filter selection.
Score breakdown
This utility's overall score of 56/100 breaks down across five weighted components. Read the full methodology →
Contaminants detected — international standards comparison
Every contaminant detected, compared side-by-side against US EPA legal limits, the EU Drinking Water Directive (2020/2184), WHO Guidelines, and California's Public Health Goal (the strictest US benchmark). 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 (4th ed.), California OEHHA PHGs, EWG Tap Water Database.
DENNIS WATER DISTRICT service area
This water system serves 1 community in Barnstable County, Massachusetts. Click any city for its dedicated tap water quality page.
Find the right filter for DENNIS water
Browse filter categories by water-quality concern. Each option below is NSF-certified for the matched contaminant type.