How They Work
The height of the tower provides the hydrostatic pressure for the water supply system. The volume of the reservoir and the diameter of the piping regulate water pressure and flow rate. As the water level in the tank drops, a ballcock lets more water into the tank, in a design similar to a toilet, as described in greater detail in InterNACHI's article on that subject.
Water towers can be constructed from a variety of materials, such as steel, concrete or wood. The towers are usually spherical or cylindrical, but custom shapes are available to suit unique needs. Some water towers are quite large and serve whole communities, although, in certain areas, such as New York City, smaller water towers are constructed for individual buildings. Ornate coverings and fancy brickwork may be used to cover what may otherwise be an eyesore, or they may be simply painted. Some municipal water towers have the name of the city painted in large letters on the roof as a navigational aid to aviators.
Water towers are used for the following purposes:
Water Towers in New York City
Perhaps nowhere are water towers such an ingrained, yet anachronistic, element of a cityscape as in New York City. The robust steel and glass skyline there is dotted with small wooden water towers that are easy to mistake for vanishing relics of a bygone era. Many New Yorkers don’t realize, however, that these towers are not antiques –- most people drink, brush their teeth and bathe from the water they provide every day.
Made from wood that is neither painted nor chemically treated, New York’s water towers appear old as a necessary consequence of safeguarding potable water from contamination. They are still made from wood rather than more modern-looking metal, because metal is often prohibitively expensive. Even so, many New Yorkers have found value in the quaint, traditional feel that these towers convey, reminding a cutting-edge city of its past. In the New York community of Tribeca, water towers are required on all buildings regardless of whether or not they are functional.
The original water tower builders were barrel makers who expanded their craft to meet a modern need, as city buildings grew taller. Water towers were necessary to prevent the need for excessively high water pressure at lower heights, which could burst pipes. Today, New York water towers are all made by one of two local, family-owned companies -- Rosenwach Tank Company and the Isseks Brothers. Rosenwach has about 10,000 tanks in the city, and can build up to 300 a year — though they’ve been sluggish lately, as has much of the construction industry.
When the towers are filled for the first time they leak, but the wood quickly swells into a leak-proof membrane that will hold for 30 to 35 years. InterNACHI inspectors need only be concerned with leaking water towers, which probably need to be replaced. A crew of six men can tear down an old tank and install a new one in about 24 hours. It then takes several hours for pumps to fill them with water. Water exits from the top of the tank instead of the bottom, where natural sediments gradually accumulate. Periodic maintenance must be performed to remove natural sediments that accumulate at the base of the tank.