Community Water System · PWS CA4310018
City of Cupertino
Operator location San Jose, California - 100% of 15 violations are health-based (upper-third health share (> 23%)); surface water source; 16,336 served per SDWIS.
- 16,336
- People served (this PWS)
- 15
- EPA violations (this PWS)
- 15
- Health-based (this PWS)
- No PFAS
- UCMR5 (this PWS)
City of Cupertino standing, low SDWIS violation third
100% of 15 recorded violations are health-based - upper-third health share (> 23%). Corpus terciles use 29,740 systems serving 500+ (the sitemap cohort). Health-based share 100% is upper-third health share (> 23%). UCMR5: UCMR5 tested, none detected. Population rank #3,207 of 29,740 among systems serving 500+.
The verdict
City of Cupertino is in the lower third by violation count (15; lower-third violation load (≤ 21 violations)). A low count does not mean the system is unmonitored - monitoring and reporting violations still appear in SDWIS. Population served is large (16,336; larger served population (> 3,309)), so household exposure scale sits behind the violation mix. Health-based share is 100% - most of this ledger is MCL or treatment-technique exceedance. UCMR5 tested this system and reported no PFAS above the minimum reporting level.
- #3,207 of 29,740
- Population · /systems
- #388 of 1,701
- Population · CA
- 15
- Total EPA violations on record
- 100%
- Health-based (MCL / treatment failure)
Population ordinals match the sitemap cohort (systems serving 500+, population_served DESC). See methodology · corpus placement.
System Details
- System Type
- Community
- Owner Type
- Local
- Connections
- 4,692
- County
- Santa Clara
- School/Daycare
- No
- MCL Violations
- 15
- Monitoring Violations
- 0
- Treatment Tech Violations
- 0
Violation History
Contaminant violations recorded by EPA.
| Contaminant | Category | Count | Latest |
|---|---|---|---|
| TTHM | MCL | 15 | 1993 |
Violation Count vs. the National Corpus
City of Cupertino has 15 recorded EPA violations, 25% of the 29,740 public water systems serving 500+ people nationwide carry fewer, and 74% carry more. 100% of this system's own violations are health-based (15 of 15), and it ranks #3,207 of 29,740 by population served among that same cohort.
EPA violations vs. the national water-system corpus
Public water systems serving 500+ people (EPA SDWIS)
15 Lower than most fewer violations than 74% of 29,740 water systems
the national water-system corpus, bucketed by value
Each bar is a band; taller bars hold more water systems. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source EPA SDWIS · 2026-05-15
PFAS Testing Results (UCMR5)
Results from EPA's Fifth Unregulated Contaminant Monitoring Rule. 0 of 149 samples detected PFAS.
| Contaminant | Date | Result | MRL | Status |
|---|---|---|---|---|
| NMeFOSAA | 9/13/2023 | <6.00 ppt | 6.00 ppt | Not Detected |
| PFTA | 9/13/2023 | <8.00 ppt | 8.00 ppt | Not Detected |
| NEtFOSAA | 9/13/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFTrDA | 9/13/2023 | <7.00 ppt | 7.00 ppt | Not Detected |
| NMeFOSAA | 9/13/2023 | <6.00 ppt | 6.00 ppt | Not Detected |
| PFTrDA | 9/13/2023 | <7.00 ppt | 7.00 ppt | Not Detected |
| NEtFOSAA | 9/13/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFTA | 9/13/2023 | <8.00 ppt | 8.00 ppt | Not Detected |
| 11Cl-PF3OUdS | 8/17/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFEESA | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| 6:2 FTS | 8/17/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| ADONA | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| HFPO-DA | 8/17/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFBA | 8/17/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| 9Cl-PF3ONS | 8/17/2023 | <2.00 ppt | 2.00 ppt | Not Detected |
| 4:2 FTS | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| 8:2 FTS | 8/17/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFMPA | 8/17/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFHpS | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHpA | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFPeS | 8/17/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFMBA | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFPeA | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFUnA | 8/17/2023 | <2.00 ppt | 2.00 ppt | Not Detected |
| NFDHA | 8/17/2023 | <20.00 ppt | 20.00 ppt | Not Detected |
| PFHxS | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFOS | 8/17/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFOA | 8/17/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFDA | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFDoA | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFBS | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHxA | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFNA | 8/17/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFEESA | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFMBA | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFPeS | 8/17/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFHpS | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHpA | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHxS | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFNA | 8/17/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFOS | 8/17/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFOA | 8/17/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFDA | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFDoA | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHxA | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| HFPO-DA | 8/17/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| 8:2 FTS | 8/17/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| 4:2 FTS | 8/17/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFMPA | 8/17/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFUnA | 8/17/2023 | <2.00 ppt | 2.00 ppt | Not Detected |
Health-based violations on City of Cupertino
15 health-based rows in the tables above map to MCL or treatment-technique exceedances, verify each contaminant code on the federal SDWIS report for CA4310018.
Sources: EPA SDWIS · California State Water Resources Control Board, Division of Drinking Water
Nationwide peers
15 violations · 16,336 served: nearest cross-state SDWIS matches.
Cross-state systems with similarly light violation ledgers
Nearest cross-state community systems (500+ served) by total SDWIS violations on record.
Cross-state systems with similar served population
Nearest cross-state systems by EPA SDWIS population_served (same 500+ sitemap gate).
What to do with City of Cupertino
Use this system's EPA-reported record as a starting filter, not a final verdict.
- See how every tracked system in California compares on the same EPA violation measures. California systems
- Check whether PFAS was detected at this system under UCMR5 testing. PFAS guide
- Find and compare another public water system by name or PWSID. Search systems
EPA SDWIS and UCMR5 figures are informational only, not a substitute for a certified lab test of your own tap water.