Where Past is Prologue – Greeley Square, 33rd Street and Broadway, New York, New York

New York City's skyline is dotted with wooden water towers that are easy to mistake for vanishing relics of the bygone era of seltzer bottles and street gas lamps. But what many New Yorkers don't realize is that the towers are hardly antiques. In fact, every day most of them drink and bathe from the water stored in them. This is because most buildings in the city taller than six stories need some sort of water tower and pumping system to provide sufficient water pressure to their tenants.

People mistake wooden for relics of the past because they look as though they are. While many of the towers are older than 30 years of age, even the new ones look old because they too are made of wood that isn’t painted or chemically treated (so as not to taint the drinking water).

Though the technology has become more efficient, the concept of using gravity to deliver water from a wooden tank hasn't changed in decades. And while steel tanks are an option, they are more expensive, don’t provide as much insulation, require more maintenance and take longer to construct. The average wood tank holds 10,000 gallons of water and costs around $30,000. A steel tank of the same size could cost up to $120,000. But different buildings have their own specific needs.

A tank can last 30-35 years depending on its exposure to the elements. Given that most weather systems move from west to east, the rooftop tanks on the west side of Manhattan typically don’t last as long because they take more of a beating. Every year a crew must clean natural sediment from the water from the bottom of the tank. Most buildings have this maintenance done in the spring and summer. Eventually, though, the wood will rot and the tank will start to leak. When this happens, a new tower must be built. With a crew of about six men, an old tank can be torn down and new one constructed in 24 hours. It takes a further two to three hours for pumps to fill them up. When first set up the towers leak, but once filled the wood expands and the tank becomes water tight.

The water towers function like giant toilets. As people use the stored water, the level goes down. A ballcock regulates how much additional water is pumped from the basement.

Who knew?