Redwood City Water Hardness & Quality Report (2026)
Water Hardness
~120–179 mg/L
Hardestimated · not lab-verified
Source
reservoir
pH Level
8.2
neutral = 7.0
Lead
0.008 mg/L
✓ Below action level
TDS
552.1 mg/L
Est. Daily Cost
$0.40
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 Redwood City, your appliances are currently losing 20% efficiency due to mineral buildup.
| Appliance | In Redwood City | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 6.8 yrs | 8.5 yrs | -20% |
| Washing Machine | 9.6 yrs | 12 yrs | -20% |
| Water Heater | 12 yrs | 15 yrs | -20% |
Regional Water Comparison
How Redwood City compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Redwood City, California | ≈ 120–179 mg/L | 0 ppt | 🟠 Hard | reservoir |
| San Carlos, California | 60 mg/L | 6.8 ppt | 🟡 Moderately Hard | mixed |
| North Fair Oaks, California | ≈ 0–60 mg/L | 4 ppt | 🟢 Soft | mixed |
| Redwood Shores, California | 32 mg/L | 7.4 ppt | 🟢 Soft | mixed |
| Belmont, California | ≈ 120–179 mg/L | 0 ppt | 🟠 Hard | reservoir |
National Benchmark
How Redwood City compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Redwood City | ≈ 120–179 mg/L | 🟠 Moderate |
| USA National Avg | 151 mg/L | 🟠 Moderate |
| Scarsdale Top Rated | 0.02 mg/L | 🟢 None |
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What Makes Redwood City's Water Unique?
Local geology and source profile
The water supply for Redwood City is managed by the City of Redwood City and drawn from two primary systems. The San Francisco Regional Water System (Hetch Hetchy Water System), operated by the San Francisco Public Utilities Commission (SFPUC), delivers water from Hetch Hetchy Reservoir in the Sierra Nevada to over 2 million Bay Area customers. Supplemental groundwater comes from Wells 1, 2, and 3 in Pescadero, operated by County Service Area No. 11, tapping the Pescadero groundwater basin. The blended supply is distributed through the city's network with continuous monitoring for chlorine residual and disinfection by-products.
The Hetch Hetchy watershed is underlain by Cretaceous and older granitic plutonic rocks of the Sierra Nevada, which impart moderate dissolved minerals to the snowmelt-fed supply. The Pescadero wells draw from Cretaceous-age sedimentary and metamorphic formations in the Santa Cruz Mountains foothills, where natural dissolution of calcium and magnesium from these rock types adds to water hardness. Together, the two sources produce a moderately hard supply characteristic of the Bay Area region.
At a moderately hard level, some scale buildup may develop in kettles, water heaters, and dishwashers over time, though effects are less severe than in hard-water areas. Water heaters and hot-water pipes are most susceptible to mineral accumulation; routine descaling and periodic flushing of water heater tanks are recommended maintenance practices. A water softener is optional but may extend appliance lifespan and improve soap efficiency. Drinking water meets all federal and state criteria; no lead service lines were identified as of October 2024, and the SFPUC maintains strict watershed protection protocols throughout the distribution network.
Geology & Source: Sierra Nevada granitic bedrock via Hetch Hetchy Reservoir; Cretaceous sedimentary and metamorphic formations in the Santa Cruz Mountains — both dissolve calcium and magnesium, producing moderately hard water
Other California Water Reports
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Frequently Asked Questions
Is Redwood City's water safe to drink?
Do I need a water softener in Redwood City?
How does Redwood City compare to the USA average?
Data Sources & Methodology
Water quality data for Redwood City 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.