Water report · not indexed
What is in the water at 91770
4 public water systems serve this ZIP code in the federal records. Everything below comes from EPA monitoring data, and everything missing is named.
SAN GABRIEL VALLEY WATER CO.-EL MONTE
PWSID CA1910039 · CA · serves 248,000 people
PFAS and lithium
2 compounds detected at or above the reporting limit under EPA’s UCMR 5 monitoring, across 2 samples.
| Compound | Highest detected | Samples | Most recent |
|---|---|---|---|
| PFBA | 0.01 µg/L | 1 | 2/28/2025 |
| PFPeA | 0.0056 µg/L | 1 | 2/28/2025 |
A detection is a measurement, not a violation and not a health finding. EPA states that UCMR 5 results do not indicate compliance or non-compliance with any limit.
Health-based violations
No open health-based violation on record. This covers MCL, treatment technique and MRDL violations in SDWIS that have not been returned to compliance. It excludes monitoring and reporting violations, which are the large majority nationally, so this is not “no violations”, and SDWIS completeness varies by state.
Hardness
Median hardness 255 mg/L as CaCO₃, measured at 8 stations serving this system across 10 results, 2015-08-13 to 2022-04-14. Measured in the water source and distribution area, not at a tap, and not in your home.
CAL/AM WATER COMPANY - SAN MARINO
PWSID CA1910139 · CA · serves 47,995 people
PFAS and lithium
2 compounds detected at or above the reporting limit under EPA’s UCMR 5 monitoring, across 5 samples.
| Compound | Highest detected | Samples | Most recent |
|---|---|---|---|
| lithium | 92 µg/L | 4 | 8/7/2023 |
| PFBA | 0.0053 µg/L | 1 | 2/7/2024 |
A detection is a measurement, not a violation and not a health finding. EPA states that UCMR 5 results do not indicate compliance or non-compliance with any limit.
Health-based violations
No open health-based violation on record. This covers MCL, treatment technique and MRDL violations in SDWIS that have not been returned to compliance. It excludes monitoring and reporting violations, which are the large majority nationally, so this is not “no violations”, and SDWIS completeness varies by state.
Hardness
No hardness measurement. Hardness is measured at environmental monitoring stations, and none fell inside this system’s service area. That is a gap in where monitoring happens, not a finding about the water.
SAN GABRIEL COUNTY WD
PWSID CA1910144 · CA · serves 39,345 people
PFAS and lithium
Sampled, nothing detected. Tested for 30 compounds under UCMR 5 with none found at or above its reporting limit. A reporting limit is the lowest concentration the method can measure, so this means “below that” rather than “zero”.
Health-based violations
No open health-based violation on record. This covers MCL, treatment technique and MRDL violations in SDWIS that have not been returned to compliance. It excludes monitoring and reporting violations, which are the large majority nationally, so this is not “no violations”, and SDWIS completeness varies by state.
Hardness
No hardness measurement. Hardness is measured at environmental monitoring stations, and none fell inside this system’s service area. That is a gap in where monitoring happens, not a finding about the water.
GSWC-SOUTH SAN GABRIEL
PWSID CA1910223 · CA · serves 26,240 people
PFAS and lithium
2 compounds detected at or above the reporting limit under EPA’s UCMR 5 monitoring, across 5 samples.
| Compound | Highest detected | Samples | Most recent |
|---|---|---|---|
| lithium | 57 µg/L | 4 | 7/9/2024 |
| PFBA | 0.0056 µg/L | 1 | 4/11/2024 |
A detection is a measurement, not a violation and not a health finding. EPA states that UCMR 5 results do not indicate compliance or non-compliance with any limit.
Health-based violations
No open health-based violation on record. This covers MCL, treatment technique and MRDL violations in SDWIS that have not been returned to compliance. It excludes monitoring and reporting violations, which are the large majority nationally, so this is not “no violations”, and SDWIS completeness varies by state.
Hardness
No hardness measurement. Hardness is measured at environmental monitoring stations, and none fell inside this system’s service area. That is a gap in where monitoring happens, not a finding about the water.
What this report cannot tell you
Every figure describes water at a sampling point: a treatment plant, an entry point to the distribution system, or a monitoring station. None of it describes water arriving at your tap. Plumbing between the two can add lead and copper, and if your home was built before 1986 a test kit tells you something no federal dataset can.
Sources: EPA UCMR 5 occurrence (final release, frozen July 2026) · EPA SDWIS health-based violations · USGS and state monitoring via the Water Quality Portal · EPA Public Water System Service Area Boundaries v3. Compiled 2026-09-01.