Water Infrastructure in San Mateo, CA: 37% Decay Risk
Decay risk 37% · moderate · 2 water systems · Updated 2026-05-03
San Mateo's infrastructure shows moderate decay risk. Some systems may need attention.
Data: EPA ECHO, Census ACS, NTSB Last verified: 2026-05-03
What is infrastructure decay probability?
Infrastructure decay probability estimates the likelihood of water pipe deterioration based on pipe age, material type, violation history, and environmental conditions. Higher probability means greater risk of water main breaks, pressure drops, and contamination from aging pipes. The national average hovers around 30-40%. San Mateo's average is 37%.
What are CO/gas incidents?
Carbon monoxide (CO) and gas incidents tracked by the NTSB include pipeline failures, gas leaks, and CO exposure events. CO is odorless and can be fatal — the CDC reports about 420 deaths annually from unintentional CO poisoning. Every home should have working CO detectors on each floor, tested monthly. San Mateo has 4 recorded incidents in the NTSB database.
Infrastructure Risk Distribution
How San Mateo's {totalZips} ZIP codes are distributed by infrastructure risk level:
Infrastructure Risk Overview
San Mateo, California has moderate infrastructure risk with an average decay probability of 37%. Some portions of the water system may require attention as infrastructure ages.
Infrastructure decay probability measures the likelihood of pipe failure, water main breaks, and system degradation based on pipe age, material, violation history, and environmental factors.
Key Infrastructure Metrics
| Metric | Value |
|---|---|
| Decay probability | 37% |
| Risk level | moderate |
| Water systems | 2 |
| Median build year | 1964 |
| Pre-1986 housing | 79% |
| CO/gas incidents | 4 |
| ZIP codes | 5 |
| Population | 157 |
Infrastructure Risk Distribution
How San Mateo's 5 ZIP codes are distributed by infrastructure risk level:
| Risk Level | ZIP Codes | Percentage |
|---|---|---|
| Low | 0 | 0% |
| Moderate | 3 | 60% |
| High | 2 | 40% |
| Very High | 0 | 0% |
40% of San Mateo's ZIP codes have high or very-high infrastructure risk. Residents in these areas should be especially vigilant about water quality and pipe condition.
Water System Age and Pipe Materials
The median home in San Mateo was built in 1964 (approximately 62 years old). Housing age is one of the strongest proxies for water infrastructure age, as service lines and interior plumbing were typically installed during construction.
Pipe material risks by era:
| Era | Common Pipe Material | Expected Lifespan | Key Risk |
|---|---|---|---|
| Pre-1940 | Lead, cast iron | 50-75 years | Lead contamination, corrosion |
| 1940-1960 | Galvanized steel, cast iron | 40-60 years | Rust, lead solder, reduced flow |
| 1960-1980 | Copper, galvanized steel | 50-70 years | Lead solder (pre-1986), pinhole leaks |
| 1980-2000 | Copper, PVC, CPVC | 25-50 years | Chlorine degradation of plastics |
| 2000+ | PEX, copper, CPVC | 25-50+ years | Generally low risk |
With 79% of San Mateo's homes built before 1986, a significant portion of residential plumbing may contain lead solder or aging pipe materials.
Carbon Monoxide & Gas Safety
4 CO/gas incidents have been recorded in the county covering San Mateo. The average CO risk score is 2 out of 100.
Carbon monoxide is odorless and colorless — it is the leading cause of poisoning deaths in the U.S. Risk factors include:
- Gas furnaces, water heaters, and stoves
- Attached garages
- Blocked chimneys or vents
- Portable generators used indoors
Prevention:
- Install CO detectors on every level, especially near bedrooms
- Have gas appliances inspected annually
- Never run generators, grills, or cars in enclosed spaces
- Replace CO detectors every 5-7 years
What Homeowners Can Do
Pipe Inspection
- Hire a licensed plumber to inspect your service line and interior plumbing
- Check for discolored water (brown/orange = rust; white/cloudy = air or sediment)
- Test water pressure — low pressure may indicate buildup in aging pipes
- Look for visible corrosion on exposed pipes in basement or utility areas
Water Heater Maintenance
- Flush your water heater annually to remove sediment
- Check the anode rod every 2-3 years (prevents tank corrosion)
- Set temperature to 120F to prevent scalding and reduce energy use
- Replace water heaters older than 10-15 years proactively
CO Detector Placement
- One detector per floor, minimum
- Within 10 feet of each bedroom door
- Near attached garage and utility room
- 5 feet above the floor (CO rises with warm air) or on the ceiling
- Not near windows, doors, or HVAC vents (air movement causes false readings)
San Mateo vs. Nearby California Cities
How San Mateo's infrastructure compares to nearby cities:
| City | Water Systems | Violations | Population |
|---|---|---|---|
| San Mateo | 2 | 20 | 157 |
| Auberry | 2 | 1 | 160 |
| Browns Valley | 1 | 0 | 160 |
| Caspar | 1 | 0 | 160 |
ZIP Codes in San Mateo
San Mateo covers 5 ZIP codes served by 2 water systems. Infrastructure condition varies by ZIP code based on housing age, pipe material, and water system maintenance. Check your specific ZIP code for localized data.
Data Sources
- Water systems: EPA ECHO — Enforcement and Compliance History Online
- Infrastructure risk: Derived model (housing age, violation history, system assessments)
- Housing age: U.S. Census Bureau American Community Survey (ACS)
- CO/gas incidents: NTSB, PHMSA pipeline incident reports
Updated daily.
Water Quality Map: San Mateo, CA
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Infrastructure Risk by ZIP Code in San Mateo
Infrastructure risk varies across San Mateo's 5 ZIP codes based on system age, pipe materials, and violation history.
| ZIP Code | Grade | Score | Violations | |
|---|---|---|---|---|
| 94401 | C | 66/100 | 4 | View report → |
| 94402 | C | 66/100 | 4 | View report → |
| 94403 | C | 66/100 | 4 | View report → |
| 94404 | C | 66/100 | 4 | View report → |
| 94497 | C | 68/100 | 4 | View report → |
Check your water system's infrastructure
Infrastructure risk varies by ZIP code and water system. Enter your ZIP for a personalized infrastructure assessment.
Check Your Infrastructure Risk