As a metropolis with a host of waste and pollution issues, New York City’s Department of Environmental Protection has taken many measures to ensure that the water and sewage systems are working correctly. But one thing that often gets overlooked is the ubiquitous drinking water sampling stations located in nearly every neighborhood of New York, as Mitch Waxman points out on Brownstoner Queens. According to Kate Ascher of The Works: Anatomy of a City, over 800 of such stations were installed in the late 1990s.

According to the DEP, these sampling stations, which were installed around the city at a cost of about 11 million dollars, feeds water from a nearby water main into the station, enabling the city to regularly check up on the quality of the water supply. The stations are made of heavy cast iron, says Ascher, and “inside a small copper tube conducts water from a nearby water main into a spigot  that runs into a small sink.” The samples are analyzed for bacteria, odor, pH, and a host of other quality indicators. Today, there are almost 1,000 of these heavy cast iron sampling stations in New York, and the city collects an impressive 1,200 samples from them per month.

Read more from our Cities 101 series about how stuff works in the city.