If It Ain't Broke Don't Fix It The Anatomy of Roof Tanks

As technology leaps forward, countless pieces of formerly indispensable equipment become obsolete, outdated, and replaced. In light of these technological advances, it’s interesting to think of the things that have not changed—inventions that function the same way today as they did when they were first introduced, having warded off replacement by newer, shinier incarnations. The short-list of timeless classics would have to include the Hula-Hoop, the Slinky…and the roof tank? Yes, the rooftop water tanks that dot the New York City skyline.

History Overhead

New York City’s first generation of roof tanks was built in the early 1900s to offer fire protection to the city’s taller buildings. According to Steven Silver of American Pump & Tank Lining Company in Manhattan, steam-driven pumps could only push water up a few floors, leaving the upper floors of skyscrapers with no real protection from fires. “New York City was really one of the first cities to go vertical, as far as skyscrapers go,” he says. “And back in the early 1900s—after some unfortunate fires and a lot of deaths in some of these higher buildings—the idea was to get some kind of [water] reserve on the upper floors.”

The New York City fire code is very stringent, says Andy Rosenwach, president of Rosenwach Tank Inc. in Long Island City. “One of the requirements for meeting that code is supplying a certain quantity of water on top [of buildings], as opposed to trying to design the building to have pressurized fire pumps and generators and other equipment… Anything over six stories requires either a constant pressure system or an artesian well on top of the building to gravity-feed down,” he says.

Over the past century, says David Hochhauser of Isseks Bros, Inc. in Manhattan, the design of roof tanks has not changed a whole lot, but nowadays they are getting larger. “Because of the new New York City fire code, tanks are being built much larger because they have to have the capacity [to serve] sprinkler systems. Whereas in the past a typical residential building would have a 10,000-gallon tank, nowadays we’re putting up 20,000- to 30,000-gallon tanks.”

How Do They Work?

The fact that roof tanks have not changed that much over the years is a testament to their incredibly effective design, which—in principle, at least—Is extremely simple.

“It’s wood held together by metal hoops,” Silver says, adding that rooftop tanks have been made pretty much the same way since their inception. “The design and construction of the tanks themselves hasn’t really changed much over the years. The tools and equipment that we use to install the tanks, that’s really what’s changed,” says Silver. In the past, hoops had to be tightened by hand, but now it’s a lot faster because it’s done with an electric impact gun. Likewise, the wooden staves in older tanks—typically cedar—had to be prepared by hand.

A traditional pump system in a rooftop water tank typically contains a rubberized float ball attached to a metal pole, and steel-encased high-voltage circuitry and mercury tube sensors which control the water level, the temperature, when the pump turns on or shuts off, and the security of the water supply, according to Rosenwach.

The tank is filled by a small pump in the basement, which pumps water all the way up to the tank from the city’s water main. As water is consumed in the building and the level in the tank lowers, the float switch triggers the pump to go on. Once the float switch reaches a certain level, it switches off the pump. The float switch is a similar mechanism to that of a toilet, except it is electric. And the system supplying the building with water “is a very simple gravity system,” says Silver. This gravity system is why buildings with roof tanks have better water pressure on the lower floors.

One of the newer tank systems today though is completely computerized, according to Rosenwach. These tanks use a remote-controlled floatless switch, which is a computerized microprocessor panel that is pre-programmed just like a desktop computer to operate the circuitry and switches needed for the tank’s pump to operate.

The unit uses a single, non-moving mercury-free sensor on two low-voltage wires or cables that are then suspended inside the tank. The circuitry, which is embedded into a compact steel box, doesn’t need to be near or inside the tank. Instead it can be located in the pump room or in the basement of the building where it is monitored by a superintendent or on-site maintenance staff. Because of the micro-controller technology and mercury-free sensors, the floatless switch can send real time alerts to the super or building personnel, like a security guard or a doorman. In-house building staff can monitor the tank and pump system by personal computer or the information can be forwarded via the Internet to building workers in the field through a PDA or BlackBerry device, he explains.

A Little Bit of TLC

Although the principles behind water tanks seem relatively simple, their construction and maintenance requires skilled professionals.

Replacing a tank that provides domestic water to a building can be done rather quickly—in about 10 hours. Replacement of a sprinkler tank takes an average of about two days, Rosenwach says.

“You are up at elevation, and you have to know what you’re doing,” says Hochhauser. “You need a technician. A plumber can’t do it. A super can’t do it. You have to have somebody qualified,” he says adding: “in our organization, we don’t let a man up on the tank until he’s been here about seven years.”

“The tank is listed as confined space, and the people that are going into the tank have to be licensed and trained for confined space. And they have to be, as per the New York City Building Code, certified for the cleaning of the tank,” says Rosenwach. Besides being trained to work in confined spaces, technicians also have to be trained in climbing. “Any climb is tricky, and you have to know how to access a ladder, then maneuver yourself back into the tank and down a ladder. That’s not simple.”

Tanks should last over a couple decades, depending on who you ask— anywhere from 20 to 35 years. Their lives can be prolonged a few years with non-permanent repairs. Sometimes these repairs are unsuccessful, and tanks are replaced outright to avoid a building code violation, the loss of water, or the buildup of ice, says Rosenwach. Some telltale signs that your tank may be nearing the end of the road are a spongy quality to the wood, algae growth on the outside of the tank, fibers delaminating, and—perhaps most obviously—leaking.

“When a tank comes to an age where it’s so rotten and porous and it’s no longer holding water… The basic procedure is the removal of the old tank, [and] replacing any of the plumbing connections that might have deteriorated,” says Silver.

To rebuild the tank, “you install the wooden dunnage beams, on top of the steel beams which actually support it,” and lay out the bottom of the tank, before putting up the wooden staves and tightening it all into place with the metal hoops. Next, the pump is turned on and the roof is put on.

Depending on the size of the tank, it could take a crew of up to four to six workers to complete the job. A new tank can be up and running in about a day— typically around twelve hours, according to Silver.

The fact that the installation process is relatively quick is beneficial to buildings, because as Rosenwach points out, “labor is the most expensive part of a product. This limits the amount of labor, because it goes in so quickly.” Not to mention the fact that, for residents, it’s hard to take a shower when you don’t have water.

Annual Maintenance

The building and taking down of roof tanks is done by qualified technicians, but “according to Local Law 76 of the New York City Building Code, domestic water tanks [also] have to be cleaned on a yearly basis,” says Hochhauser. The Health and Plumbing Codes also state that you have to be a licensed contractor or a licensed plumber to clean tanks. However, Hochhauser believes that having a plumber do the annual tank cleaning, instead of a roof tank technician, is potentially costly for buildings.

“Plumbers sometimes try to clean and service the water tanks,” he says. “The problem is while they’re able to clean out the tanks, they’re not able to service them—to stop leaks… All they’re doing is the cleaning portion of it. They’re not doing the full service.”

When a tank company cleans a tank, Hochhauser says, they clean it, repair it, and guarantee it against leaks. “That’s an important concept I think—when a building does procure a service contract from a qualified tank company, that tank company will guarantee the tank against leaks and will service it over the course of the year.”

Some supers may think they are getting a deal by hiring a plumber to do a tank cleaning for less than it would cost to bring in a tank company. But, says Hochhauser, “six months later, [when] the tank is leaking… they can’t call the plumber, because the plumber can’t fix [a leak.] So, they call us and we charge them for a service call.” By doing this, he contends, buildings pay extra because they are paying a plumber, in addition to paying a tank company anyway.

Regardless of whom you call in for your annual tank cleaning, the importance of roof tanks in New York City living is hard to deny. They provide us with water, protect our buildings from fire, and add an interesting accent to the famous New York City skyline. Perhaps it is the classic simplicity of the design in this computerized, technological age. Or perhaps there is something refreshing about the natural elements involved: wood and water, in a gravity system. “Wood tanks make people happy,” Rosenwach says. “No question about it.”

The New York City skyline just wouldn’t look the same without its rooftop panoply of rustic wooden water tanks. Roof tanks aren’t just interesting architectural conversation pieces; they’re working parts of your building’s operating systems and deserve care and maintenance on a regular basis.

Sam Nixon is a project manager and occasional freelance writer, living in Brooklyn.

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  • The Board of Directors of my building was told that the tank control sensor in the roof water tank needs replacing at a cost of $6,500, which includes a 10 year warranty against wear and tear. Does that sound reasonable?