New York City Water Quality Guide: Upstate Reservoirs
Comprehensive guide to NYC water quality from upstate reservoirs, filtration exemption status, treatment, and safety information.
Environmental Health Research
Health Information Reviewed
Health-related content reviewed by Michael Rodriguez, MSc, Public Health Consultant, to ensure public health recommendations are accurate and appropriate.
Last reviewed: April 2026
Water Source
New York City operates one of the world's most remarkable water supply systems, drawing from protected watersheds up to 125 miles north of the city. The system includes three main components: the Catskill and Delaware systems in the Catskill Mountains (providing about 90% of supply) and the older Croton system in Westchester and Putnam counties. Nineteen reservoirs and three controlled lakes have a total storage capacity of approximately 580 billion gallons. This gravity-fed system delivers over 1 billion gallons daily to 8.3 million city residents plus another million people in Westchester, Putnam, Orange, and Ulster counties.
Water Treatment Process
NYC is one of only four large US cities with a surface water supply pure enough to avoid filtration under EPA regulations. The Catskill and Delaware systems receive UV disinfection at the Catskill-Delaware Ultraviolet Disinfection Facility (the world's largest UV facility), chlorine for residual disinfection, fluoride for dental health, and orthophosphate for corrosion control. The Croton system, being more developed, is filtered at the new Croton Filtration Plant. The city maintains its filtration exemption through rigorous watershed protection programs covering nearly 2,000 square miles.
Known Issues and Considerations
While NYC's water is among the highest quality in the nation, some concerns exist particularly related to aging infrastructure within the city.
- Aging building plumbing can contribute lead to water
- Lead service lines exist, though fewer than many older cities
- Turbidity can temporarily increase after heavy rainfall
- Some older buildings have internal lead pipes or lead solder
- Disinfection byproducts form at low levels during chlorination
- Climate change threatens watershed protection long-term
- Croton system historically required more treatment
- Distribution system repairs can temporarily affect local quality
Recent Improvements and Investments
NYC DEP continues investing billions in water infrastructure while maintaining the watershed protection that enables the filtration exemption.
- Completed Croton Filtration Plant, the largest in the US
- Expanded UV disinfection capacity for all supplies
- Invested $2+ billion in watershed protection programs
- Upgraded distribution infrastructure throughout the city
- Enhanced lead monitoring and testing programs
- Implemented real-time water quality monitoring systems
- Developed climate adaptation strategies for watersheds
- Expanded community water testing programs
EPA Compliance and Quality Monitoring
NYC water consistently meets or exceeds all EPA drinking water standards and maintains the Surface Water Treatment Rule filtration waiver. The city conducts over 500,000 water quality tests annually at various points from watershed to tap. Lead levels at the 90th percentile have historically been below the EPA action level. DEP publishes annual Water Quality Reports and provides free testing for residents concerned about individual building conditions. The watershed protection program is recognized as a model for other cities.
Note: For the most current water quality data, view the New York City Water Quality Report which includes EPA SDWIS data and contaminant analysis.
Recommendations for NYC Residents
NYC tap water is among the best in the nation, though building-specific conditions may warrant additional precautions.
- 1Run water for 30 seconds before drinking in older buildings
- 2Check if your building has lead service lines or plumbing
- 3Use NSF-certified filters if concerned about lead in older buildings
- 4Request free water testing from DEP if concerned
- 5Review annual Water Quality Reports from DEP
- 6Report unusual taste, odor, or color immediately
- 7Avoid hot tap water for drinking or cooking
- 8Landlords must test and remediate lead in many buildings
Water Filter Options for New York City
Based on New York City's water quality profile, consider these filtration options:
Activated Carbon Filters
Good for improving taste, removing chlorine/chloramine, and filtering common organic compounds.
Reverse Osmosis Systems
Comprehensive filtration removing 95-99% of contaminants including lead, PFAS, and dissolved solids.
Related Resources
- New York City, New York Water Quality Report
View current contaminant data and quality scores
- New York State Water Quality Overview
Compare water quality across New York cities
- Home Water Testing Guide
How to test your water at home
- Complete Guide to Lead in Drinking Water
Understanding lead risks and mitigation
- How to Choose the Right Water Filter
Filter recommendations by contaminant type
- Water Filter Cost Calculator
Calculate the cost of different filtration options