How does Redwood Shores's water compare to the national average?

The USA national average is 151 mg/L. Redwood Shores (32 mg/L) is 119 mg/L softer than average.

Redwood Shores Water Hardness & Quality Report (2026)

Water Hardness

32mg/L

Soft

1.9 grains per gallon

Source

mixed

pH Level

8.3

neutral = 7.0

Lead

0.009 mg/L

✓ Below action level

TDS

580.7 mg/L

Est. Daily Cost

$0.09

energy & soap waste

Source: See methodology section below · Updated 2026

32mg/L as CaCO₃Soft

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 Shores, your appliances are currently losing 4% efficiency due to mineral buildup.

Appliance	In Redwood Shores	Soft Water City	Efficiency Loss
Kettle	8.5 yrs	8.5 yrs	—
Washing Machine	12.4 yrs	12 yrs	—
Water Heater	14.3 yrs	15 yrs	-5%

Regional Water Comparison

How Redwood Shores compares to its nearest neighbours

City	Hardness	PFAS (ppt)	Risk	Source
▶ Redwood Shores, California	32 mg/L	7.4 ppt	🟢 Soft	mixed
San Carlos, California	60 mg/L	6.8 ppt	🟡 Moderately Hard	mixed
Belmont, California	≈ 120–179 mg/L	0 ppt	🟠 Hard	reservoir
Foster City, California	32 mg/L	0 ppt	🟢 Soft	reservoir
Redwood City, California	≈ 120–179 mg/L	0 ppt	🟠 Hard	reservoir

National Benchmark

How Redwood Shores compares to the USA average

Benchmark	Hardness	Appliance Risk
▶ Redwood Shores	32 mg/L	🟢 None
USA National Avg	151 mg/L	🟠 Moderate
Scarsdale Top Rated	0.02 mg/L	🟢 None

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What Makes Redwood Shores's Water Unique?

Local geology and source profile

Source: MixedTDS: 580.7 mg/LpH: 8.3

The California Water Service Company's San Mateo System provides water to Redwood Shores, drawing from a mix of sources. These include surface water from reservoirs nestled in the Santa Cruz Mountains and local groundwater aquifers. The San Mateo System serves San Mateo County and nearby communities, including the planned area of Redwood Shores on the San Francisco Peninsula. Water treatment occurs at multiple facilities before distribution to residents.

The watershed feeding the San Mateo System covers the eastern slopes of the Santa Cruz Mountains. Here, Quaternary alluvial deposits sit atop Cretaceous and Tertiary sedimentary rocks, with a foundation of granitic and metamorphic basement rock. This geology, largely devoid of carbonate minerals, means the water supply is soft, containing little dissolved calcium and magnesium. This characteristic is common in coastal California regions shaped by granitic landscapes.

Because the water is soft, homeowners in Redwood Shores typically don't face significant issues with scale buildup in appliances like dishwashers or water heaters, nor in household pipes. You'll find that soap lathers easily, making it unnecessary for most homes to install a water softener. Keeping plumbing and appliances in good condition is usually straightforward, without the worry of mineral deposits. This softness can also be beneficial for certain industrial applications that require water with minimal hardness. Cal Water's San Mateo System consistently meets federal and state drinking water regulations, as detailed in their 2022 Water Quality Report.

Geology & Source: Coastal plain alluvial deposits and marine sediments; granitic and metamorphic bedrock result in soft water

Other California Water Reports

San Carlos

60 mg/L

🟡 Moderately Hard

Belmont

≈ 120–179 mg/L

🟠 Hard

Foster City

32 mg/L

🟢 Soft

Redwood City

≈ 120–179 mg/L

🟠 Hard

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Notice an error or missing data? Help us keep this page accurate. If you spot incorrect water hardness, outdated utility info, or missing details, please let us know.

All reports are reviewed by our team. Thank you for supporting data quality!

Frequently Asked Questions

Is Redwood Shores's water safe to drink?

Yes. Redwood Shores's water meets all federal safety standards. The hardness is 32 mg/L (Soft), which is safe to drink. High hardness affects appliances and taste, but poses no health risk.

Do I need a water softener in Redwood Shores?

Redwood Shores's water is soft at 32 mg/L. A water softener is generally not necessary, though a carbon filter can improve taste and remove any remaining chlorine.

How does Redwood Shores compare to the USA average?

The USA national average is 151 mg/L. Redwood Shores (32 mg/L) is 119 mg/L below the national average. The softest major city is Scarsdale at just 0.02 mg/L.

Data Sources & Methodology

Water quality data for Redwood Shores is derived from geographic and geological modelling of the surrounding region. No federal monitoring station data was available for this location.

Estimated

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.

Estimated

Estimated from regional geology and source water characteristics. pH is correlated with water hardness and local bedrock — values may differ from utility-reported figures.

Estimated

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.

Measured

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.

Modelled

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.

Calculated

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.