How NYC Works: Thousands of Miles of Pipes Make Up City's Complex Sewer System

In the latest installment of "How New York City Works," NY1's Roger Clark takes a look at the city's wastewater treatment system to find out what happens to all of the dirty water we send down the drain.

New Yorkers use a lot of water. An average of 1.2 billion gallons goes down the drain every day. Plus, there's everything that falls on the city when it rains or snows. All of that water, and everything else that flows down with it, has to go somewhere. So where does it all go? The only place it can. Into the waterways that surround us.

Before it reaches the waterways, it passes through a complex wastewater treatment system run by the city's Department of Environmental Protection to clean and disinfect it so we don't get sick and wildlife can survive. Let's find out how it works.

Most of the city runs on what's known as a combined sewer system, meaning everything we send down the drain or toilet, and all the rain, snowmelt and other runoff that flows into any of our 140,000 street catch basins, all wind up in the same 6,000 miles of pipes. The "combined sewage" then travels, mostly by gravity, to one of 14 wastewater treatment plants. Sometimes, it needs a little push to get there, and that's where 96 pump stations come in. We went underground to check out one station in Manhattan.

The screen room is about 30 feet below street level, and that's where the raw sewage comes in. The room is the first place that it's going to be screened.

"The sewage comes through a series of metal bars that are spaced about an inch apart, and those bars remove things like sticks, leaves, plastic bottles, rags, anything that may find its way into the sewer system," says Vincent Sapienza, a DEP Deputy Commissioner in the bureau of wastewater treatment.

That material gets a lift upstairs to be loaded into containers and taken to a landfill. Every now and then, DEP workers come across some pretty interesting finds.

The whole thing about alligators living in the sewer system is an urban legend, but there is another type of reptile that somehow made its way into this pumping station: turtles. The workers are taking good care of them.

For the remaining sewage, it's on to the next step.

"The sewage that you see here, Roger, is now getting pumped up several stories into a surge tower, and then, by gravity, that can then flow to the next station in the treatment process, which is the Newtown Creek Plant in Brooklyn," Sapienza says.

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How NYC Works: Thousands of Miles of Pipes Make Up City's Complex Sewer System