Water Quality Report · Updated May 12, 2026
MARIN MUNICIPAL WATER DISTRICT
MARIN MUNICIPAL WATER DISTRICT delivers tap water graded C (67/100) by TapWaterSafety.org. The utility serves approximately 186,895 residents in CORTE MADERA, California using surface water. The most significant water quality concerns are: Haloacetic acids (HAA5) 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 415-945-1557.
Is CORTE MADERA tap water safe to drink?
MARIN MUNICIPAL WATER DISTRICT delivers tap water that earns a grade of C (67/100) from TapWaterSafety.org — an average rating, with several contaminants above health guidelines but generally compliant with US legal limits.
The utility serves 186,895 residents in CORTE MADERA, drawing from surface water.
Public testing data identifies 10 contaminants in this water above EWG's health-based guidelines, including: Haloacetic acids (HAA5), Haloacetic acids (HAA9), Total trihalomethanes (TTHMs), Bromodichloromethane, Trichloroacetic acid, Dibromochloromethane, Chloroform, Dichloroacetic acid, Dibromoacetic acid, Chromium (hexavalent). 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 CORTE MADERA residents
Top concerns in this water
Based on the most recent EPA and EWG data, these are the most significant water quality issues for MARIN MUNICIPAL WATER DISTRICT.
Haloacetic acids (HAA5) significantly above health guideline
Moderate concernHaloacetic acids (HAA5) detected at 36.2 ppb, 362x above the EWG health guideline of 0.1 ppb.
Haloacetic acids (HAA9) significantly above health guideline
Moderate concernHaloacetic acids (HAA9) detected at 21.0 ppb, 350x above the EWG health guideline of 0.06 ppb.
Total trihalomethanes (TTHMs) significantly above health guideline
Moderate concernTotal trihalomethanes (TTHMs) detected at 32.2 ppb, 215x above the EWG health guideline of 0.15 ppb.
Contact MARIN MUNICIPAL 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 CORTE MADERA
Filters matched to the specific contaminants in this water supply.
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 67/100 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 |
|---|---|---|---|---|---|---|---|---|
| Haloacetic acids (HAA5) Disinfection byproduct |
36.2 ppb | 0.1 | 60.0 | 60 | — | — | — | 362× over |
| Haloacetic acids (HAA9) Disinfection byproduct |
21.0 ppb | 0.06 | — | — | — | — | — | 350× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
32.2 ppb | 0.15 | 80.0 | 100 | — | — | — | 215× over |
| Bromodichloromethane Disinfection byproduct |
9.88 ppb | 0.06 | — | — | — | — | — | 165× over |
| Trichloroacetic acid Disinfection byproduct |
6.38 ppb | 0.1 | — | — | — | — | — | 64× over |
| Dibromochloromethane Disinfection byproduct |
4.92 ppb | 0.1 | — | — | — | — | — | 49× over |
| Chloroform Disinfection byproduct |
17.1 ppb | 0.4 | — | — | — | — | — | 43× over |
| Dichloroacetic acid Disinfection byproduct |
7.02 ppb | 0.2 | — | — | — | — | — | 35× over |
| Dibromoacetic acid Disinfection byproduct |
0.784 ppb | 0.03 | — | — | — | — | — | 26× over |
| Chromium (hexavalent) Heavy metal |
0.0542 ppb | 0.02 | — | — | — | — | — | 2.7× over |
| Bromoform Disinfection byproduct |
0.27 ppb | 0.5 | — | — | — | — | — | Below guideline |
| Nitrate and nitrite Inorganic |
0.0524 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | Below guideline |
| Chlorate Disinfection byproduct |
61.6 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Nitrate Inorganic |
0.0148 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | Below guideline |
| Vanadium Other |
0.0834 ppb | 21.0 | — | — | — | — | — | Below guideline |
| Monochloroacetic acid Disinfection byproduct |
0.171 ppb | 53.0 | — | — | — | — | — | Below guideline |
| Strontium Radiological |
0.103 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Fluoride Inorganic |
0.221 ppm | — | 4.0 | 1.5 | 1.5 | — | — | Below guideline |
| o-toluidine Other |
0.0014 ppb | — | — | — | — | — | — | 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.
MARIN MUNICIPAL WATER DISTRICT service area
This water system serves 1 community in Marin County, California. Click any city for its dedicated tap water quality page.
Find the right filter for CORTE MADERA water
Browse filter categories by water-quality concern. Each option below is NSF-certified for the matched contaminant type.