San Marino Water Hardness & Quality Report (2026)
Water Hardness
8.2 grains per gallon
Source
groundwater
pH Level
7.3
neutral = 7.0
Lead
0.002 mg/L
✓ Below action level
TDS
93 mg/L
Est. Daily Cost
$0.37
energy & soap waste
Source: See methodology section below · Updated 2026
0–60
mg/L
Soft
61–120
mg/L
Moderately Hard
121–180
mg/L
Hard
180+
mg/L
Very Hard
Appliance Damage Report
In San Marino, your appliances are currently losing 19% efficiency due to mineral buildup.
| Appliance | In San Marino | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 5 yrs | 8.5 yrs | -41% |
| Washing Machine | 8.4 yrs | 12 yrs | -30% |
| Water Heater | 10 yrs | 15 yrs | -33% |
Regional Water Comparison
How San Marino compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ San Marino, California | 140 mg/L | 3.2 ppt | 🟠 Hard | groundwater |
| San Gabriel, California | ≈ 180+ mg/L | 7.3 ppt | 🔴 Very Hard | mixed |
| Alhambra, California | ≈ 180+ mg/L | 0 ppt | 🔴 Very Hard | reservoir |
| East San Gabriel, California | ≈ 180+ mg/L | 6.3 ppt | 🔴 Very Hard | mixed |
| South Pasadena, California | ≈ 180+ mg/L | 0 ppt | 🔴 Very Hard | reservoir |
National Benchmark
How San Marino compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ San Marino | 140 mg/L | 🟠 Moderate |
| USA National Avg | 151 mg/L | 🟠 Moderate |
| Scarsdale Top Rated | 0.02 mg/L | 🟢 None |
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What Makes San Marino's Water Unique?
Local geology and source profile
California American Water provides treated surface water purchased from the Metropolitan Water District of Southern California's Weymouth Water Treatment Plant, supplemented by groundwater from the Main San Gabriel and Raymond Basins. The service area covers the City of San Marino in Los Angeles County, extending to portions of San Gabriel, Temple City, South Pasadena, Pasadena, and unincorporated Los Angeles County areas, serving approximately 41,241 residents. Treatment involves chloramination for the surface water and chlorine disinfection for groundwater bacteriological control. The watershed encompasses the Upper San Gabriel River drainage and imported aqueduct supplies from the Colorado River and California State Water Project.
The groundwater originates from the unconfined and semi-confined aquifers of the San Gabriel Valley, shaped by alluvial fan deposits from surrounding San Gabriel Mountains. These formations, including fractured bedrock aquifers influenced by granitic weathering and carbonate dissolution, impart a hard character to the water through natural mineral leaching. Surface imports add variable mineralization from diverse terrains, including limestone and evaporite formations along the Colorado River's path and ancient lakebeds. This geological mix results in naturally mineralized, hard water typical of Southern California's inland valleys.
Hard water in this supply leads to moderate scale buildup in appliances like water heaters, dishwashers, and washing machines, reducing efficiency over time and increasing energy costs. Faucets and fixtures may develop limescale rings, and laundry can feel stiff without softeners. Regular vinegar descaling, installing drain screens, and using high-efficiency appliances mitigate effects; a water softener is recommended for households with noticeable spotting on glassware or film on skin after bathing to extend appliance life and improve cleaning results. Fluoride averages 0.8 mg/L, maintained at 0.6-0.8 ppm via state standards.
Geology & Source: Main San Gabriel Basin & Raymond Basin aquifers; Quaternary alluvial deposits, San Dimas Formation (limestone, dolomite); Colorado River Aqueduct (limestone, evaporites) - moderate to hard water
Other California Water Reports
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Frequently Asked Questions
Is San Marino's water safe to drink?
Do I need a water softener in San Marino?
How does San Marino compare to the USA average?
Data Sources & Methodology
Water quality data for San Marino is derived from geographic and geological modelling of the surrounding region. No federal monitoring station data was available for this location.
Water Hardness
Modelled estimate based on state-level USGS geological survey data for this region. No direct USGS Water Quality Portal measurement was matched to this city — the value reflects a statistical range calibrated to the state's dominant rock types and typical source water characteristics.
pH
Estimated from regional geology and source water characteristics. pH is correlated with water hardness and local bedrock — values may differ from utility-reported figures.
TDS — Total Dissolved Solids
Estimated using a derived ratio from water hardness and regional conductance profiles. TDS in natural water correlates strongly with total mineral content including hardness ions.
PFAS — Perfluoroalkyl and Polyfluoroalkyl Substances
EPA UCMR5 (5th Unregulated Contaminant Monitoring Rule, 2023–2025) — sum of PFAS compounds detected at the public water system serving this city. A value of 0 indicates the system was sampled with no detection above reporting limits.
Lead
Modelled estimate based on the EPA Lead and Copper Rule 90th-percentile tap-sample methodology. No publicly available per-city lead dataset with sufficient national coverage exists. Values are a conservative baseline derived from city population tier and infrastructure age — all estimates are maintained below the EPA action level of 0.015 mg/L.
Appliance Lifespan
Calculated from water hardness using a linear degradation model. Baseline lifespans represent soft-water performance (kettle: 8.5 yrs, washing machine: 12.0 yrs, water heater: 15.0 yrs). Hard water mineral scale progressively reduces operational life in direct proportion to hardness concentration.