Drinking water quality

About Drinking water quality

All NYC residences receive drinking water from a public water system. Most water is gravity fed from a network of reservoirs and lakes in protected watersheds, up to 125 miles from the city.

The NYC water system consists of two surface water systems: Croton and Catskill/Delaware and one groundwater system, in Southwestern Queens. Since 1999, the Croton system has served as a supplemental water system. The Catskill/Delaware reservoir system supplies almost all NYC drinking water. For more on how NYC gets and tests its water, read the 2022 Drinking Water Supply & Quality report.

We display data on disinfection by-products, nitrates, and arsenic in NYC drinking water because these contaminants occur most frequently at levels that may be of public health significance in drinking water nationwide.

Drinking Water Quality and Health

The New york Department of Environmental Protection (DEP) regularly samples, analyzes and reports contaminant levels at the source and in the drinking water distribution system. Monitoring drinking water is important because contamination in a single system could exposes many people at once. People can be exposed to contaminants in many ways besides drinking the water. They can also be exposed through eating food prepared with the water, breathing water droplets or chemicals released from the water while showering, or by absorbing chemicals through their skin while bathing.

Lead: According to the DEP, drinking water enters the NYC water system “virtually lead-free.” The DEP then uses anti-corrosion methods to reduce the leaching of any lead that may be present in plumbing fixtures, solder, or pipes, which connect the water system to buildings in NYC. Federal regulations require that lead testing of water is done at the tap of a sample of NYC buildings each year.

Disinfection by-products: Drinking water is disinfected to reduce the possibility of illness from microorganisms. Disinfection by-products (DBPs) are chemicals that can form when a disinfectant such as chlorine reacts with naturally occurring organic matter and other substances in the source water. Current research is looking at whether there are health effects from chronic exposure to the by-products of water disinfection.

Nitrates: Nitrates are commonly found in water near where nitrogen-based fertilizers are used. Decades ago, it was discovered that infants who were fed formula made with water containing nitrates over 10 mg/L sometimes became seriously ill, due to the interference of nitrate with the oxygen-carrying capacity of blood.

Arsenic: Arsenic is naturally occurring in groundwater systems in some parts of the US. It may also enter drinking water systems through past use of arsenic-containing pesticides and wood preservatives. Chronic exposure may increase risk of certain cancers. It is not detected in NYC drinking water.

About the Data and Indicators

The data presented here provide summary measures of contaminants in drinking water sampled at many points in the distribution system.


  • Most people do not need to take any actions to prevent water-related illnesses or health effects from drinking NYC water.
  • Though levels of contaminants are consistently very low in water that arrives to a building, lead or lead-soldered plumbing in some older buildings may raise lead levels in water at the tap. Reducing the possibility of exposure to lead in drinking water is simple and inexpensive. Run your tap for at least 30 seconds, until the water is noticeably colder, before drinking, cooking or making baby formula. Free tap water quality tests are available by calling 311.
  • Ultimately, maintaining the highest quality drinking water depends on protecting our lakes, rivers and aquifers from contamination.

Key Messages

The quality of the drinking water in the NYC system is excellent. The water systems serving NYC are consistently in compliance with EPA guidelines.

DBP concentrations show a seasonal effect with higher concentrations during the warm and rainy months when more organic material is in the water systems. Arsenic levels are consistently very low in NYC. Nitrate levels are also consistently low, owing to the protection of upstate watersheds from farm runoff.

NYC drinking water has many advantages over bottled water or processed beverages. Its sources are known, and its purity is checked. It is not stored in plastics, and it doesn’t get shipped in vehicles that pollute the air. It costs little or nothing, and it is calorie-free.

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