Ontario Tap Water Quality Report
Ontario's water has 5 contaminants above EPA MCLGs. We recommend using a certified water filter.
Other systems listed for Ontario with results above guidelines: CUCAMONGA VALLEY WATER DISTRICT (1 above guidelines)
Water system
ONTARIO MUNICIPAL UTILITIES COMPANY
1 other system is listed for Ontario. See its figures
People Served
185,010
Health-based violations since 2020
0
ONTARIO MUNICIPAL UTILITIES COMPANY. EPA SDWA violation data as of Q2 2026 (downloaded 2026-07-09).
Latest sample on file
Sep 2025 · ONTARIO MUNICIPAL UTILITIES COMPANY
Utilities publish newer results in their annual water quality report (Consumer Confidence Report).
Is Ontario Tap Water Safe to Drink?
We strongly recommend using a certified water filter to reduce exposure: Ontario's water has 5 contaminants above EPA health-based guidelines. Check our filter recommendations below for NSF-certified options that can remove the specific contaminants found in Ontario's water.
ONTARIO MUNICIPAL UTILITIES COMPANY, Ontario's water system, serves 185,010 people. 1 other system is listed for Ontario. Each system's results are listed under its own name, never added to ONTARIO MUNICIPAL UTILITIES COMPANY's. Water quality testing is conducted regularly and reported to the EPA. The latest sample on file for ONTARIO MUNICIPAL UTILITIES COMPANY is from Sep 2025.
Boil water advisories are issued by water systems and state agencies, and they change from day to day. Boil water advisories in California
Ontario Water Service Areas
What these numbers actually mean for Ontario, CA
We read Ontario, CA’s published record and send you a short report — which findings warrant a decision, which to ignore, and what to do about it. Including when the answer is nothing.
- 5 contaminants above EPA MCLGs and 5 contaminants with an EPA health goal detected in some samples (no level on file)
- 54 results on file
- 23 PFAS compounds on record
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Recommended Water Filters for Ontario
Based on Ontario's water quality data, these NSF-certified filters are recommended to remove contaminants above EPA MCLGs.
Culligan
ZeroWater
NSF Certified:
Flow Rate
1.9 gpm
Daily Production
1 gpd
Highlights:
- Compact design
- Easy to set up
- Affordable
- NSF-42, NSF-53, NSF-401 certified
Removes 19 contaminants:
+14 more
Strontium, Molybdenum, Fluoride, Uranium, Lead, Total PFAS, Chlorine, 25, Phosphorus, Bicarbonate, Calcium, Carbonate, Magnesium, Sodium
Santevia
Bath Filter
NSF Certified:
Flow Rate
0.36 gpm
Highlights:
- Organic cotton design reduces plastic used in construction
- Affordable upfront & ongoing cost
- The only bath filter that removed 100% chlorine with “normal” faster faucet flow
Removes 1 contaminants:
Waterdrop
A1
NSF Certified:
Flow Rate
1 gpm
Highlights:
- Performance certified
- Lower price than Philips
- Hot water dispensing
- Compact design
Removes 5 contaminants:
Whirlpool Corporation
W11256135
NSF Certified:
Capacity
1001 gal
Filter Life
3 mo
Flow Rate
0.7 gpm
Removes 19 contaminants:
+14 more
Benzene, Carbofuran, Chlorine (Free), Chlorine (Total), Chlorine Dioxide, Chlorobenzene, Cryptosporidium, Ethylbenzene, Lead, Mercury, Metolachlor, Tetrachloroethylene, Toxaphene, Turbidity
Verify Your Water Quality with Independent Testing
With 5 contaminants above EPA MCLGs and 5 contaminants with an EPA health goal detected in some samples (no level on file), independent laboratory testing provides a second opinion and can track changes over time.
SimpleLab
Advanced Home Water Test
$269
Comprehensive water analysis testing over 200 contaminants including bacteria, heavy metals, and chemical compounds.
Tap Score
PFAS Forever Chemicals Test
$339.95
Specialized test for PFOA, PFOS, and 24 other forever chemicals. Essential for areas near military bases, airports, or industrial sites.
Tap Score
Advanced Microplastics Test
$829
Cutting-edge testing for microplastics particles in drinking water using advanced laboratory techniques.
With 5 contaminants above health guidelines, you may want to explore water purification options. Learn how to make distilled water at home for applications like humidifiers, CPAP machines, and baby formula.
What Ontario's water readings can explain
Utility-reported data for Ontario includes sulfate and a chlorine-based disinfectant — the readings behind these common tap water questions. We publish a city-level hardness figure for Ontario, resolved from its water systems where they report one and estimated from county sampling where they do not. Each page starts with the hot-tap and cold-tap check, then shows what your own water system reported.
On a private well near Ontario? Public-water results do not apply to private wells. See San Bernardino County well water testing and USGS risk data — modeled arsenic, nitrate, and the tests to run.
Water softener cost and installation in Ontario
Ontario's tap water measures 7.4 grains per gallon (127.0 mg/L) — hard on the USGS scale, the range where scale on fixtures and appliances is the usual complaint.
Water softener cost for 7.4 gpg water in Ontario — equipment and local installation labour for your ZIP code, with the sizing arithmetic shown in full. For the national picture first, read what a water softener costs — equipment, installation labour and ten-year ownership, each separated out. For California as a whole, read water softener cost in California — priced against the plumber wage published for the state.
Frequently Asked Questions About Ontario Tap Water
Ontario's water has 5 contaminants above EPA MCLGs. We strongly recommend using a certified water filter to reduce exposure to these contaminants. Check our filter recommendations below for NSF-certified options that can remove the specific contaminants found in Ontario's water.
Spotted something off on this page?
Residents keep our data honest.
This form corrects our data; it does not reach ONTARIO MUNICIPAL UTILITIES COMPANY. For a problem with your water now (discolored water, no water, low pressure, a leak), contact ONTARIO MUNICIPAL UTILITIES COMPANY directly.
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