Billings Water Quality at a Glance
major concerns
Is Billings Water Safe to Drink?
Generally Yes, With Major Cautions — While Billings water meets federal compliance standards, it contains arsenic at 1,250 times above EWG health guidelines and elevated levels of multiple cancer-causing disinfection byproducts. The Yellowstone River source continues to be affected by upstream industrial discharge, including arsenic from the CHS refinery in Laurel, Montana. See our full U.S. water quality guide for context on how Billings compares nationally.
⚠️ Key Concerns for Billings Residents
- Arsenic: Cancer-causing heavy metal at 5.00 ppb — 1,250x above EWG health guidelines
- Chromium-6: Carcinogenic hexavalent chromium detected at 6.6x above California health guidelines
- Disinfection Byproducts: Multiple cancer-causing compounds from chlorine treatment including chloroform (78x over guidelines) and total trihalomethanes (278x over guidelines)
- Source Contamination: Yellowstone River impacted by ongoing industrial arsenic discharge from the CHS refinery in Laurel
Read the full report below for detailed analysis, contamination sources, and actionable recommendations for Billings residents.
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Billings, Montana — Water Quality Report 2026: Arsenic Contamination, Disinfection Byproducts & Safety Across Your City
Billings Public Works provides comprehensive water services to approximately 115,000 residents in Montana‘s largest city and surrounding areas, including portions of Yellowstone County. As a municipal utility serving the Magic City, the system operates approximately 800 miles of water distribution lines, multiple storage reservoirs, and advanced treatment facilities that deliver an average of 50 million gallons of drinking water daily to residents and businesses across the greater Billings metropolitan area.
Billings sources its drinking water exclusively from the Yellowstone River, the longest free-flowing river in the contiguous United States. The water is treated at the historic Belknap Water Treatment Plant, which has served the community since 1914 and undergone numerous modernizations to achieve a current capacity of 60 million gallons per day. While Billings’ water meets federal compliance standards, testing continues to reveal significant concerns: arsenic levels 1,250 times above EWG health guidelines, and multiple cancer-causing disinfection byproducts. The Yellowstone River source remains impacted by upstream industrial discharge from the CHS refinery in Laurel, creating ongoing water quality challenges that require enhanced treatment and continued monitoring through 2026.
Billings Water Quality: Current Status (2025–2026)
Latest Testing Results
- Water Quality Compliance: Billings water remains in compliance with federal health-based drinking water standards. However, federal legal limits for many contaminants have not been substantially updated in decades and do not reflect current health science or the latest EPA guidance introduced in 2024–2025.
- Arsenic Contamination: Third-party testing found arsenic at 5.00 ppb — 1,250 times above EWG health guidelines (0.004 ppb), though still below the federal legal limit of 10 ppb. Arsenic remains the single most pressing water quality concern for Billings residents.
- Disinfection Byproducts: Multiple cancer-causing compounds continue to be detected, including chloroform (78x above health guidelines), bromochloroacetic acid (125x above guidelines), and total trihalomethanes (278x above guidelines).
Water Sources
- Yellowstone River: Billings’ sole water source, drawing from the 671-mile river that originates in Yellowstone National Park and flows through the city. The river faces ongoing contamination pressure from upstream industrial activities.
- Upstream Contamination: The CHS refinery in Laurel has been discharging arsenic into the Yellowstone River since at least 2015. Arsenic discharge from the refinery has been measured at levels ranging from 6 to 80 micrograms per liter — well above state water quality standards — and enforcement actions have continued into the mid-2020s.
- Source Water Challenges: The river experiences extreme seasonal fluctuations — from historic flooding to drought conditions — while also carrying industrial contaminants from upstream sources, making consistent treatment more demanding.
Treatment Technology
- Belknap Water Treatment Plant: The facility, originally established in 1914 and continuously upgraded, uses conventional treatment processes — coagulation, flocculation, sedimentation, filtration, and chlorine disinfection — with a capacity of 60 million gallons per day.
- Treatment Limitations: Current treatment processes are effective for basic microbial safety but do not adequately reduce arsenic or prevent the formation of disinfection byproducts, which are created when chlorine reacts with organic matter in the source water.
- Monitoring and Testing: Ongoing monitoring continues under EPA and Montana DEQ requirements. Testing results consistently show multiple contaminants above modern health guidelines, even while remaining within legal compliance thresholds. Check our live U.S. boil water advisory tracker for any active emergency notices in Billings.
Infrastructure Modernization
- West End Water Treatment Plant: The long-planned $68 million project to provide backup treatment capacity and enhanced emergency reserves — increasing from hours to weeks of supply — has been progressing through construction phases. When complete, it will significantly improve system resilience against supply disruptions.
- Lead Service Line Replacement: Billings completed its EPA-mandated lead service line inventory by the October 2024 deadline and continues active replacement of approximately 320 identified lead service lines under the updated Lead and Copper Rule. For context on lead risk across Montana, older homes built before 1986 remain most vulnerable.
- Smart Meter Rollout: Neptune 360 smart meters continue to be deployed across the service area, improving real-time water usage monitoring and helping the utility detect leaks and system inefficiencies more rapidly.
Contamination Sources and Challenges
Billings faces significant water quality challenges stemming from both natural and industrial sources. The primary concern is arsenic contamination, which is substantially elevated by upstream industrial discharge from the CHS refinery in Laurel — a facility that has been releasing arsenic into the Yellowstone River since at least 2015, with discharge levels averaging 34 micrograms per liter and far exceeding state water quality standards. Additionally, the chlorine disinfection process creates cancer-causing byproducts when it reacts with organic matter in the river water, including chloroform, bromochloroacetic acid, and total trihalomethanes. The utility’s reliance on a single-source water system makes Billings particularly vulnerable to upstream contamination events and seasonal variations in source water quality. Residents looking for actionable guidance should visit our water filter solutions guide for NSF-certified options tailored to these specific contaminants.
Recommendations for Billings Residents
Install Water Filtration
Given the significant arsenic contamination and disinfection byproducts in Billings water, we strongly recommend installing an NSF-certified reverse osmosis or activated carbon filtration system. Reverse osmosis is most effective for arsenic removal, while carbon filters can reduce chlorine byproducts. See our complete water filter guide for the top-rated options for Montana’s water chemistry.
Request Water Testing Data
Contact Billings Public Works at 406-657-8345 to request the most recent Consumer Confidence Report and specific data about contaminant levels in your area. Ask specifically about arsenic levels and disinfection byproduct concentrations for your neighbourhood. The city is required by law to provide this information.
Check Your Service Lines
Use Billings’ Water Service Line Material Viewer at billingsmtpublicworks.gov to identify your service line material by address. For homes built before 1986, consider additional point-of-use testing given the city’s current contamination concerns and ongoing lead service line replacement programme.
Advocate for Better Treatment
Contact Billings city officials and attend public utility meetings to advocate for enhanced water treatment technologies — particularly advanced oxidation or enhanced coagulation — that can better address arsenic and reduce disinfection byproduct formation. Supporting stricter enforcement against the CHS refinery’s upstream discharge is equally important for long-term source water quality in Montana.
Stay Informed About Contamination
Monitor news about the CHS refinery’s arsenic discharge compliance and any updates to Billings water treatment improvements. Bookmark our live U.S. boil water advisory tracker for real-time emergency alerts, and check our water quality news section for the latest developments in Montana and nationally.
Frequently Asked Questions
Is Billings tap water safe to drink in 2026?
Billings tap water meets all current federal compliance standards but contains concerning levels of contaminants that exceed modern health guidelines. The water contains arsenic at 1,250 times above EWG health guidelines and multiple cancer-causing disinfection byproducts that exceed health-protective thresholds.
While the city’s water treatment process addresses basic safety requirements, it does not effectively remove arsenic or prevent the formation of disinfection byproducts. Federal legal limits for many contaminants have not kept pace with current scientific understanding of health risks. Residents — particularly those who are pregnant, elderly, or immunocompromised — should consider additional filtration for long-term consumption. See our water filter solutions page for recommendations suited to Billings’ contamination profile.
What is causing the arsenic contamination in Billings?
The primary source of elevated arsenic is the CHS refinery in Laurel, upstream of Billings’ Yellowstone River intake:
• Industrial discharge: CHS has released arsenic at 6–80 micrograms per liter into the Yellowstone River, averaging 34 micrograms per liter
• Ongoing compliance issues: The refinery was given deadlines to meet compliance standards but enforcement challenges have continued into the mid-2020s
• Location impact: Billings draws water downstream from Laurel, directly exposing its intake to contaminated discharge
• Natural background: Some arsenic occurs naturally in Montana geology, but industrial discharge significantly elevates levels above natural baselines
The EPA drinking water standard for arsenic is 10 micrograms per liter, but health experts and state guidelines recommend far lower levels for long-term safety.
What are disinfection byproducts and why are they concerning?
Disinfection byproducts (DBPs) are chemicals formed when chlorine — used to kill bacteria — reacts with naturally occurring organic matter in the Yellowstone River source water:
• Formation process: Chlorine reacts with dissolved organic compounds during water treatment, producing DBPs as an unintended side effect
• Health concerns: Many DBPs are classified as probable carcinogens linked to bladder, colon, and rectal cancers with long-term exposure
• Compounds detected in Billings: Chloroform, bromochloroacetic acid, total trihalomethanes, and haloacetic acids — several at 78–849 times above health guidelines
• Prevention: These compounds are largely preventable through alternative disinfection methods (such as UV or ozone) or enhanced source water treatment, but Billings’ current processes continue to generate them at concerning levels
What filtration systems work best for Billings water?
Given Billings’ specific contamination profile, different filtration technologies address different concerns. Visit our water filter solutions guide for detailed, independently reviewed recommendations.
For Arsenic Removal:
• Reverse osmosis systems (most effective — removes 90–99% of arsenic)
• Ion exchange filters
• Look for NSF/ANSI Standard 58 (reverse osmosis) or NSF-53 certification for arsenic reduction
For Disinfection Byproducts:
• Activated carbon block filters
• Reverse osmosis systems
• Look for NSF-53 certification for trihalomethane and haloacetic acid reduction
Best Overall Protection: A whole-house or under-sink reverse osmosis system addresses both arsenic and disinfection byproducts simultaneously and is the most comprehensive option for Billings households.
Quality News About Your Water
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Contaminants of Concern
Arsenic Contamination
Source: Industrial discharge from the CHS refinery in Laurel releasing 6–80 micrograms per liter of arsenic into the Yellowstone River upstream of Billings’ water intake, compounded by naturally occurring arsenic in regional geology across Montana
Health Effects: Chronic arsenic exposure increases risk of skin, bladder, lung, kidney, and prostate cancers. Even low-level long-term exposure can cause health problems, particularly in children and other vulnerable populations
Current Levels: 5.00 ppb detected in Billings water — 1,250 times above California and EWG health guidelines (0.004 ppb), though below the federal legal limit of 10 ppb. Filtration Needed: Reverse osmosis or NSF-53 certified ion exchange systems. See our filter guide for specific product recommendations.
Disinfection Byproducts
Source: Formation when chlorine disinfectant reacts with organic matter in Yellowstone River water during treatment, creating cancer-causing compounds as an unintended consequence of standard disinfection practice
Health Effects: Probable carcinogens that increase cancer risk with long-term exposure; may cause reproductive and developmental problems. Linked to bladder, colon, and rectal cancers in multiple epidemiological studies
Current Levels: Chloroform (78x above guidelines), total trihalomethanes (278x above guidelines), haloacetic acids (333–849x above guidelines). Filtration Options: Activated carbon block and reverse osmosis systems certified under NSF-53 for trihalomethane and haloacetic acid reduction
Chromium-6 (Hexavalent Chromium)
Source: Industrial pollution and natural occurrences in mineral deposits and groundwater — the same carcinogenic compound featured in the Erin Brockovich case that contaminated Hinkley, California. Present in Billings water at low but health-relevant levels
Health Effects: Classified as a human carcinogen by multiple health agencies. A 2008 National Toxicology Program study found chromium-6 in drinking water caused cancer in laboratory animals at levels relevant to human exposure
Current Levels: 0.131 ppb detected — 6.6 times above California health guidelines (0.02 ppb) established to protect against cancer. Treatment Options: Reverse osmosis and ion exchange filtration systems are most effective for chromium-6 removal
PFAS Status — 2026 Update
Current Status: Earlier EPA monitoring found no detections of PFAS compounds above laboratory reporting limits in the Billings public water system, placing Billings among Montana communities without confirmed PFAS contamination. However, new testing requirements under EPA’s UCMR5 rule have expanded PFAS monitoring nationally and results continue to be updated.
New 2024–2025 Federal Standards: The EPA finalised enforceable Maximum Contaminant Levels (MCLs) for six PFAS compounds in April 2024 — the first federal drinking water standards ever set for PFAS. Water utilities, including those in Montana, have until 2029 to achieve compliance, with ongoing UCMR5 monitoring data being published as it becomes available.
Statewide Context: In Montana, Kalispell and Hamilton have previously detected PFAS in public water supplies, with Kalispell recording elevated levels at contaminated wells. Billings residents should continue to monitor Montana DEQ updates as broader UCMR5 sampling data is released through 2026. Track any emergency notices via our live boil water advisory tracker.
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