Is Ontario, CA Tap Water Safe to Drink?
Ontario tap water meets federal Safe Drinking Water Act standards but 3 of 3 ZIP codes show detections above EPA health guidelines, primarily for PFTrDA. A certified filter is recommended for households that want an additional layer of protection.
Where Does Ontario Get Its Water?
Water in Ontario, CA is provided by 5 public water systems: ONTARIO MUNICIPAL UTILITIES COMPANY, CUCAMONGA VALLEY WATER DISTRICT, BRYAN CO. RWS & SWMD #2, MONTE VISTA CWD and WESTERN MWD.
How Is Ontario Tap Water Treated?
Treated water is disinfected using free chlorine and calcium hypochlorite and chloramines. Treatment includes air stripping, conventional treatment (coagulation, flocculation, and filtration), direct filtration, granular activated carbon filtration, groundwater disinfection, ion exchange, post-ozone biofiltration and slow sand filtration.
What's in Ontario Tap Water?
The following contaminants were detected most frequently in Ontario public water systems. 3 of 3 ZIP codes showed detections above EPA health guidelines.
| Contaminant | Peak detected | EPA guideline | ZIPs detected | Status |
|---|---|---|---|---|
| PFTrDA | 0.007 µg/L | 0.007 µg/L | 3 ZIPs | Above guideline |
| lithium | 9 µg/L | — | 0 ZIPs | Within guideline |
| 8:2 FTS | 0.005 µg/L | — | 0 ZIPs | Within guideline |
| 11Cl-PF3OUdS | 0.005 µg/L | — | 0 ZIPs | Within guideline |
| 6:2 FTS | 0.005 µg/L | — | 0 ZIPs | Within guideline |
Health Risk Profile for Ontario
Based on EPA monitoring data, 3 of 3 ZIP codes in Ontario have recorded detections above EPA health guidelines. Sensitive populations such as infants, pregnant individuals, and those with weakened immune systems may benefit from an additional layer of protection such as a certified point-of-use filter.
Best Broad-Spectrum Filters for This Water Profile
This city profile includes PFAS detections, chlorine disinfection, and other dissolved contaminants. Reverse osmosis (RO) systems certified under NSF/ANSI 58 provide broad reduction coverage; for PFAS specifically, confirm NSF/ANSI P473 or equivalent PFAS reduction certification.
8-stage tankless RO system certified to NSF/ANSI 58, reduces 1,000+ contaminants including PFAS, lead, arsenic, fluoride, and nitrates.
See recommendations matched to your exact address: choose your ZIP code below.
Frequently Asked Questions about Ontario Tap Water
Is Ontario tap water safe to drink?
Ontario tap water meets Safe Drinking Water Act requirements but 3 of 3 ZIP codes show contaminant levels above EPA health-based guidelines. A certified point-of-use filter adds an extra layer of protection.
What contaminants are in Ontario tap water?
The most commonly detected contaminants in Ontario water systems include: PFTrDA, lithium, 8:2 FTS. See the ZIP-level reports for exact measurements and EPA guideline comparisons.
Where does Ontario get its drinking water?
Ontario receives water from 5 public water systems, including ONTARIO MUNICIPAL UTILITIES COMPANY.
Do I need a water filter in Ontario?
If your ZIP code is among those with detections above EPA health guidelines, choose a filter certified for the specific contaminants shown in your ZIP report. Reverse osmosis is generally the broadest option for PFAS, lithium, and many other dissolved contaminants.
How often is Ontario tap water tested?
Public water systems in Ontario are required by the EPA to test for regulated contaminants on schedules ranging from daily (for microbials and disinfectants) to annual or triennial (for many chemical contaminants). Results are published in annual Consumer Confidence Reports (CCRs). The data on this page reflects the most recent available EPA monitoring results, with the latest sample date of 2025-11-12.
Tap water reports by ZIP in Ontario
- 91761 - Creekside, Ontario tap water report Higher concern
- 91762 - Ontario CCD, Ontario tap water report Higher concern
- 91764 - Guasti, Ontario tap water report Higher concern
Water utilities serving Ontario, CA
Service area boundaries are approximate and based on state filings or modeled estimates. Contact your utility to confirm exact service at a specific address.
- ONTARIO MUNICIPAL UTILITIES COMPANYAction advised
Also covers / overlaps with
- Ontario CCD, CA · Township
- San Bernardino CCD, CA · Township