Water Quality in San Dimas, CA: No Violations — Grade A
Grade A · Score 95/100 · 5 water systems · Updated 2026-05-03
San Dimas's water meets all EPA standards with no health-based violations.
Data: EPA Safe Drinking Water Information System (SDWIS) Last verified: 2026-05-03
A clean federal EPA record is what the data shows for San Dimas, CA — 5 systems tracked across the full available compliance history, with no MCL exceedances, no unresolved monitoring gaps, and no enforcement proceedings documented at any stage.
Water Quality by ZIP Code in San Dimas
Water quality varies across San Dimas's 1 ZIP codes. Check your specific ZIP for detailed contaminant data.
| ZIP Code | Grade | Score | Violations | Health | |
|---|---|---|---|---|---|
| 91773 | B | 83 | 0 | 0 | View report → |
Water Quality Overview
San Dimas, California receives a water quality grade of A with an overall score of 95 out of 100, based on EPA compliance data from the Safe Drinking Water Information System (SDWIS).
No EPA violations have been recorded for the 5 water systems serving San Dimas. This is a positive indicator, though it does not guarantee the absence of all contaminants — some substances (like PFAS) are not yet fully regulated.
What Grade A Means
A grade of A indicates excellent compliance with EPA drinking water standards. San Dimas's water systems have maintained strong performance in both contaminant monitoring and regulatory compliance.
Lead Levels
The average 90th percentile lead level across San Dimas water systems is 0.0032 mg/L — within EPA limits. No ZIP codes exceed the EPA lead action level.
With 77% of homes built before 1986, San Dimas has a higher-than-average risk of lead from older plumbing. Lead solder was banned in 1986, and homes built before this date may have lead in pipes, solder joints, or fixtures.
Water Systems Serving San Dimas
San Dimas is served by 5 community water systems regulated under the Safe Drinking Water Act. These systems collectively serve approximately 156,943 people across 1 ZIP codes.
Each water system is identified by a Public Water System ID (PWSID) and is required to:
- Test for over 90 regulated contaminants on a regular schedule
- Report results to the EPA and state regulators
- Issue an annual Consumer Confidence Report (CCR) to all customers
- Take corrective action when violations occur
The EPA has taken 2 enforcement actions against water systems serving San Dimas. Enforcement actions range from informal compliance assistance to formal orders and penalties.
How to Check Your Water in San Dimas
Enter your ZIP code on ZipCheckup to see your specific water system data, including contaminant levels, violation history, and safety scores
Request your CCR — your water utility must provide an annual Consumer Confidence Report with detailed test results for all monitored contaminants
Get a home test — certified kits cost $20–$50 and test for lead, bacteria, and common contaminants. Professional lab tests ($150–$400) cover a broader panel
Consider filtration — NSF-certified filters can remove specific contaminants. Reverse osmosis removes the broadest range; activated carbon is effective for chlorine and many organics
Check for advisories — monitor your local utility website and local news for boil water advisories or system alerts
EPA Enforcement History
The EPA and state regulators have taken 2 enforcement actions against water systems serving San Dimas. Recent actions:
| Date | Action Type |
|---|---|
| 2022-09-13 | State Filed Suit |
| 2021-05-18 | State Order Extension |
Enforcement actions range from informal compliance assistance to formal orders and penalties. The most recent action was on 2022-09-13.
San Dimas vs. Nearby California Cities
How San Dimas's water quality compares to similar cities in California:
| City | Grade | Violations | Systems | Population |
|---|---|---|---|---|
| San Dimas | A | 0 | 5 | 156,943 |
| Sunnyvale | B | 0 | 1 | 157,566 |
| Roseville | B | 3 | 5 | 155,825 |
| Rialto | B | 0 | 2 | 158,951 |
Common Questions About San Dimas Water
These are the most common questions residents search for about water quality in San Dimas, California:
Is San Dimas water hard or soft? Water hardness varies by source. San Dimas's 5 water systems use multiple sources. Check your ZIP code report for specific hardness data.
Can I drink San Dimas tap water? San Dimas's water receives a grade of A (95/100). No health-based violations have been recorded, but home testing is always recommended.
What is the best water filter for San Dimas? A NSF/ANSI 53-certified filter for lead removal is a good general choice. See our Water Filter Matcher for personalized recommendations.
San Dimas vs. California Average
Understanding how San Dimas compares to the broader California average helps contextualize your local water quality. Factors like water source, treatment methods, and infrastructure age all contribute to differences between cities in the same state.
To see how individual neighborhoods compare, check the ZIP code reports below — water quality can vary significantly even within San Dimas.
ZIP Codes in San Dimas
San Dimas spans 1 ZIP code. Each ZIP code has its own water quality profile based on the specific water system serving that area. Check each ZIP code for detailed contaminant data, violation history, and system information.
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Lead/copper: EPA Lead and Copper Rule sampling data
- Radon: EPA Map of Radon Zones
- Enforcement: EPA ECHO database
- Filter recommendations: NSF/ANSI certified products
Updated daily.
Frequently Asked Questions
Your Water is Safe — Here's How to Keep It That Way
Grade A is excellent news. Here's what proactive homeowners do to maintain water quality:
Annual Water Testing
EPA recommends annual testing even with clean water. Home test kits: $20-$50. Catches changes before they become problems.
Maintenance Filtration
A basic carbon filter removes chlorine taste and catches emerging contaminants like PFAS that aren't yet fully regulated.
Plumbing Check
Even safe city water picks up lead from home pipes. If your home was built before 1986, a one-time pipe inspection is recommended.