NYC Sewer System

Learn about the history of NYC's sewer system, how it functions, and its importance to human and ecosystem health.

Before New York City transformed into the bustling metropolis we know today, it was a lush, green landscape. With changes to both the land and population came many challenges, like managing our water resources. Just as we developed a drinking water supply to ensure the health of residents, we also needed to develop ways to dispose of our waste. Let's explore how we built an effective system to collect our waste and ensure clean water is returned safely to the environment. Download the  Student Worksheet  to follow along.

Mannahatta: A Green Landscape

Mannahatta, or "the land of many hills," was the Lenni-Lenape name for what would eventually become Manhattan. This natural, lush landscape of trees, shrubs, wetlands, and wildlife was cultivated by the Lenape tribe until the Dutch colonists arrived in 1606.

[Image: Illustrated by Markley Boyer, The Mannahatta Project, Wildlife Conservation Society]

New York City: An Urban Landscape

Over the next few centuries, more people moved into what would become New York City, and apartment buildings, offices, schools, and sidewalks, were built as a result.

This removed much of the vegetation and wetlands that made up our natural environment. Impervious surfaces, or surfaces that are not able to absorb water, replaced our green landscape.

As NYC developed, it became clear that we needed a comprehensive system to collect and treat all of our wastewater and stormwater runoff.

History of the NYC Sewer System

By the early 1800s, NYC's population was rapidly increasing. More people meant more waste to clean up. Increased development also meant that impervious surfaces covered much of the natural landscape, creating excess water runoff each time it rained. Due to growing unsanitary conditions and threats to public health and the local ecosystem, it became clear that we needed to build a sewer system to collect our wastewater and stormwater runoff.

Bedpans and Human Health

Before indoor plumbing became standard in the mid 1800s, it was common for residents to throw the contents of bedpans and washbasins directly out their windows. Rotting trash and dead animals would also sit on the streets for days. This contaminated the local water supply which led to outbreaks of waterborne diseases, such as cholera and dysentery.

As we learned in the NYC Watershed Virtual Tour, in 1842, NYC began delivering safe and clean drinking water from upstate NY. Around the same time, the city's first sewers were built to remove wastewater.

This notice warned people about the spread of cholera. [Image: New-York Historical Society, published by order of the Sanatory Committee, under the sanction of the Medical Counsel (NY, 1849)]

Draining Waste to Waterways

Early on, we constructed open canals to help protect residents and transport wastewater away from where people lived and into larger bodies of water. The Broad Street canal, built by the early Dutch settlers in Lower Manhattan, became NYC’s first open sewer (and was later covered and buried underground).

While these early sewers reduced the amount of waste on the streets, the release of untreated wastewater directly impacted the ecological health of our waterways.

[Image: NYC Municipal Archives, Department of Public Works]

Impacting New York Harbor

Unfortunately, sending waste to waterways led to poor water quality, foul odors, the closure of commercial shellfish beds, and ongoing outbreaks of waterborne illnesses.

To tackle this problem, the New York Metropolitan Sewerage Commission (MSC) began to study wastewater discharges and determine improvements for sanitary conditions. The MSC conducted the first surveys of harbor water quality, which led to the establishment of a Harbor Survey Program in 1909.

To learn more, visit the Harbor Water Quality Virtual Tour.

Conveying Wastewater for Treatment

As local waterways became highly polluted, the public called for action. Dr. George Soper, a sanitary engineer and leader of the MSC, helped push for the construction of a proper sewer system and wastewater treatment facilities.

By the early 1900s, NYC constructed its first three facilities to treat wastewater. We also built large-capacity sewers, called interceptors, to “intercept” wastewater discharging to waterways and carry it to facilities for treatment. Treatment, however, only relied on screening and sedimentation (removing solids that float and sink), and was not enough to improve water quality around the harbor.

[Image: NYC Municipal Archives, Department of Public Works]

Improving Wastewater Treatment

Over the next 100 years (1886-1987), NYC would upgrade its wastewater treatment process and build an additional 11 wastewater resource recovery facilities to manage the increased wastewater from a growing population.

By improving the wastewater treatment system, we also saw dramatic changes to the health of our waterways. (seen here: Tallman Island Wastewater Resource Recovery Facility in 1974)

Expanding the Sewer System

Over time, we expanded the sewer system to encourage proper drainage and carry wastewater to the 14 wastewater resource recovery facilities for treatment.

While sewers rely primarily on gravity to convey wastewater, we needed to build pumping stations in low-lying areas to help lift the wastewater up so it could continue flowing by gravity to the nearest facility.

Today, NYC's sewers collect 1.3 billion gallons of wastewater on dry days and up to 3.6 billion gallons of wastewater and stormwater runoff during wet weather.

NYC's Sewer System Today

Today, we manage a complex system of sewer pipes, catch basins, and pumping stations, that collect and carry our wastewater and stormwater runoff. To learn more about the wastewater treatment process, visit the Wastewater Treatment Virtual Tour.

Continue reading to find out how wastewater and stormwater are transported through the sewer system.

Wastewater

Wastewater includes all of our used water and waste that goes down the drains from homes, schools, and businesses.

Imagine what goes down your drains at home! Human waste (poop!), food scraps, cooking grease, toilet paper, and other household waste flows down your drains and into the sewer system.

Stormwater Runoff

Stormwater runoff is any water from rain or snowmelt that runs off streets, sidewalks, rooftops, and other impervious surfaces. This runoff flows to catch basins and then enters the sewer system.

Often, stormwater sweeps up pollutants, such as car oil, litter or trash, and pet waste. What types of litter do you see on the ground in your neighborhood?

NYC has more than 144,000 catch basins to capture stormwater runoff from our streets.

Types of Sewers

NYC has two types of sewer systems, the combined sewer system and the separate sewer system.

There are more than 7,500 miles of sewers pipes beneath NYC. If you unraveled our underground sewers, you could stretch them from New York to California and back again!

Combined Sewer System

In a combined sewer system, wastewater and stormwater runoff are collected together in the same sewer pipe. About 60% of NYC relies on the combined sewer system, which is mostly found in older areas, such as Manhattan, Bronx, and parts of Brooklyn and Queens.

Typically, all of our wastewater and stormwater runoff is directed to the nearest wastewater resource recovery facility.

Combined Sewer Overflow

However, during heavy wet weather, a mix of untreated stormwater and wastewater may be released directly to local waterways. These events are called Combined Sewer Overflows (CSOs). A CSO can negatively impact harbor water quality and harm aquatic wildlife.

A sign warns of the location of a CSO outfall, where untreated water may enter waterways during heavy wet weather.

Municipal Separate Storm Sewer System

In a separate sewer system, one pipe carries stormwater runoff to the nearest waterway, while another pipe carries wastewater separately to the nearest wastewater resource recovery facility.

Referred to as the Municipal Separate Storm Sewer System (MS4), these storm sewers are typically found in newer and low-lying areas, such as southeast Queens, south Brooklyn, and Staten Island.

Although, wastewater does not mix in with the stormwater, other pollutants, like litter and pet waste, can still flow directly out to waterways.

Which type of sewer system serves your neighborhood?

Check out the map on the right, using the above legend.

Staten Island Bluebelts

DEP's Staten Island Bluebelts are engineered wetlands that naturally manage stormwater that runs off streets and sidewalks. We preserve natural streams, ponds, and wetlands, and enhance them to help drain, store, and filter stormwater runoff.

Bluebelts also provide open green space for communities and a diverse habitat for wildlife to thrive.  Learn more .

Protecting Our Sewers

Given the variety of waste that can end up in our sewers, some items can cause more damage than others. For example, fatbergs, a mixture of grease, wet wipes, and other household waste products can form in our sewer pipes and interrupt the flow of wastewater. View the slideshow below to find out how we inspect and maintain the sewer system.

Sewer Inspection and Maintenance

DEP sewage treatment workers maintain and improve sewers across NYC. They check that wastewater and stormwater are properly collected and able to flow to the nearest wastewater resource recovery facility.

Sewage Treatment Workers

In order to check the sewers, sewage treatment workers often need to open sewer covers and climb down into the pipes below ground.

Sewer Back-ups

Sewage treatment workers may find clogs, like a fatberg, in a sewer pipe, which can cause sewer back-ups if they are not removed.

Fatbergs

The term fatberg combines the words fat and iceberg to describe the mix of congealed grease and personal hygiene products that have been found floating in and clogging sewers around the world, including NYC.

NYC Sewer System Improvements

Engineers and sewage treatment workers work together to improve our sewer system. This includes installing new sewer pipes and improving sewer pumping stations.

Cleaning Catch Basins

Catch basins that collect stormwater can also become clogged with street litter and leaves. Sewage treatment workers clear the debris to ensure stormwater flows into the catch basin and to prevent street flooding.

So how do we clean a catch basin?

Watch the video to find out!

How can you help?

As you've just learned, the NYC Department of Environmental Protection works to maintain and improve our sewer system. However, we can all work together to protect our sewers. Continue reading to learn how you can help.

Trash It. Don't Flush It.

Trash It. Don't Flush It.

When we flush or drain household waste, like cooking grease and wet wipes, we can end up clogging our pipes and the sewers beneath our street. Remember that these clogs, or fatbergs, can cause sewer back-ups and damage to our sewer system.

Watch the video to find out which types of waste can be flushed, and which should be trashed.

Don't Trash Our Waters

Keep Our Waters Trash-Free

When it rains, stormwater runoff picks up litter and other contaminants on streets and sidewalks and flows into the sewers. Such trash can clog catch basins and cause street flooding. Polluted stormwater can also end up flowing directly to our waterways untreated. Help protect our sewers and New York Harbor by recycling when possible and throwing litter in trash cans.

Activities and Resources

Check out some of the activities and resources below to continue learning about NYC's sewer system and how we can all help it function properly.

  • What is a watershed? Simply put, a watershed is an area of land that collects water. We all live in a watershed, even in NYC! Use this activity to think about the ways water drains in NYC, into the sewers and into waterways.
  • Explore the watershed in your own neighborhood, and compare it to the landscape of our drinking watersheds.
  • Complete the Secrets of the Sewers Worksheet, while you watch the Secrets of New York episode below about the sewers and wastewater treatment system.

NYC Media

For more activities and resources, visit  DEP's website  and the  Sewer System Education Module .

Glossary

Combined Sewer Overflow (CSO) - A mix of excess stormwater runoff and untreated wastewater that discharges from combined sewers to waterways. CSOs generally occur during heavy rain or snowmelt when wastewater resource recovery facilities reach capacity.

Combined sewer system - A sewer system designed to collect and carry wastewater and stormwater runoff together to wastewater resource recovery facilities.

Fatberg - A combination of the words “fat” and “iceberg” to describe the masses of congealed grease and personal hygiene products that can clog sewer pipes and damage wastewater treatment equipment.

Impervious surface - A surface, or an area, which water cannot seep in or pass through.

Municipal Separate Storm Sewer System (MS4) - A sewer system that collects stormwater runoff from properties and streets, and discharges it directly to surrounding waterways.

Sewer - A pipe or conduit that carries wastewater and stormwater from the source to a treatment facility or receiving waterway.

Separate sewer system - A sewer system designed to collect wastewater and stormwater runoff separately, carrying wastewater to wastewater resource recovery facilities and stormwater runoff directly to waterways.

Stormwater runoff - The precipitation that falls on streets, sidewalks, and rooftops and flows overland, rather than being absorbed naturally into the ground.

Wastewater - The used water mixed with solid waste that flows down the drains from homes, schools, and businesses. Also referred to as "sewage."

We encourage you to check out more  NYC Water Virtual Tours . We would also love to hear from you, please take a moment to  share your feedback  on our virtual tours.

Copyright New York City Department of Environmental Protection. Please contact DEP's Education Office at educationoffice@dep.nyc.gov with any questions.

NYC Sewer System Virtual Tour

New York City Department of Environmental Protection

Don't Trash Our Waters

This notice warned people about the spread of cholera. [Image: New-York Historical Society, published by order of the Sanatory Committee, under the sanction of the Medical Counsel (NY, 1849)]

NYC has more than 144,000 catch basins to capture stormwater runoff from our streets.

A sign warns of the location of a CSO outfall, where untreated water may enter waterways during heavy wet weather.

Check out the map on the right, using the above legend.