Tap Water Quality Report
Tap water quality in SAN DIMAS, California
Tap water in SAN DIMAS, California receives a grade of D (67/100) from TapWaterSafety.org. It's served by GSWC-SAN DIMAS. 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; Arsenic detected. Data sources: EPA SDWIS, EPA ECHO, EWG Tap Water Database.
What's in SAN DIMAS's tap water
Top water quality concerns identified by the EPA and Environmental Working Group across the utility serving SAN DIMAS.
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 15.1 ppb, 251x above the EWG health guideline of 0.06 ppb.
Total trihalomethanes (TTHMs) significantly above health guideline
Moderate concernTotal trihalomethanes (TTHMs) detected at 24.6 ppb, 164x above the EWG health guideline of 0.15 ppb.
Arsenic detected
Moderate concernArsenic detected at 0.267 ppb.
EPA compliance record
Official U.S. EPA records for GSWC-SAN DIMAS (system ID CA1910142) 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 SAN DIMAS
Filters matched to the specific contaminants in SAN DIMAS's water supply.
Carbon filter certified for VOCs (NSF/ANSI 53)
$180-$599Activated carbon is effective for disinfection byproducts. Look for NSF/ANSI 53 VOC reduction.
Reverse osmosis certified for arsenic (NSF/ANSI 58)
$429-$599Reverse osmosis certified under NSF/ANSI 58 for arsenic is the most reliable home option.
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 SAN DIMAS'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 |
|---|---|---|---|---|---|---|---|---|
| Haloacetic acids (HAA5) Disinfection byproduct |
36.2 ppb | 0.1 | 60.0 | 60 | — | — | — | 362× over |
| Haloacetic acids (HAA9) Disinfection byproduct |
15.1 ppb | 0.06 | — | — | — | — | — | 251× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
24.6 ppb | 0.15 | 80.0 | 100 | — | — | — | 164× over |
| Bromodichloromethane Disinfection byproduct |
7.19 ppb | 0.06 | — | — | — | — | — | 120× over |
| Dibromochloromethane Disinfection byproduct |
8.35 ppb | 0.1 | — | — | — | — | — | 83× over |
| Arsenic Heavy metal |
0.267 ppb | 0.004 | 10.0 | 10 | 10 | 0.004 | — | 67× over |
| Dibromoacetic acid Disinfection byproduct |
1.74 ppb | 0.03 | — | — | — | — | — | 58× over |
| Nitrate and nitrite Inorganic |
4.7 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 34× over |
| Nitrate Inorganic |
4.34 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 31× over |
| Dichloroacetic acid Disinfection byproduct |
4.95 ppb | 0.2 | — | — | — | — | — | 25× over |
| Chloroform Disinfection byproduct |
6.67 ppb | 0.4 | — | — | — | — | — | 17× over |
| Chromium (hexavalent) Heavy metal |
0.332 ppb | 0.02 | — | — | — | — | — | 17× over |
| Trichloroacetic acid Disinfection byproduct |
1.68 ppb | 0.1 | — | — | — | — | — | 17× over |
| Uranium Radiological |
2.86 pCi/L | 0.43 | 20.0 | 30 | 30 | 0.43 | — | 6.7× over |
| Bromoform Disinfection byproduct |
2.73 ppb | 0.5 | — | — | — | — | — | 5.5× over |
| Chlorate Disinfection byproduct |
73.6 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Vanadium Other |
3.25 ppb | 21.0 | — | — | — | — | — | Below guideline |
| Molybdenum Other |
4.0 ppb | 40.0 | — | — | — | — | — | Below guideline |
| Barium Heavy metal |
68.8 ppb | 700.0 | 2000.0 | — | 1300 | 2000 | — | Below guideline |
| Manganese Heavy metal |
1.7 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Aluminum Heavy metal |
5.0 ppb | 600.0 | — | 200 | — | 600 | — | Below guideline |
| Monobromoacetic acid Disinfection byproduct |
0.165 ppb | 25.0 | — | — | — | — | — | Below guideline |
| Monochloroacetic acid Disinfection byproduct |
0.255 ppb | 53.0 | — | — | — | — | — | Below guideline |
| Strontium Radiological |
0.634 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Chlorodifluoromethane Other |
0.0556 ppb | — | — | — | — | — | — | Below guideline |
| Fluoride Inorganic |
0.626 ppm | — | 4.0 | 1.5 | 1.5 | — | — | 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 GSWC-SAN DIMAS.