- The Washington Times - Thursday, May 16, 2002

Todd Supple and Jeff Asner are standing in front of a wall-to-wall mosaic of lines, blinking lights and drawings of water towers of all shapes and sizes.
Behind them, two engineers study computer screens and weather maps with green blobs moving across them. The green blobs are thunderstorms, as any fan of the Weather Channel would recognize, and they are making Mr. Supple and Mr. Asner slightly nervous.
"You never know what's going to happen in a thunderstorm or when the next emergency is going to come because of it," Mr. Asner says. "The tanks really come in handy in situations like this, with potential thunderstorms coming. It's a lot less worry for us and our customers."
Mr. Supple and Mr. Asner are civil engineers for the Washington Suburban Sanitary Commission, which supplies water for about 1.6 million persons in Montgomery and Prince George's counties. The tanks they are discussing are water towers, landmarks that date back to the Old West.
People drive by them every day without thinking about them. Nevertheless, water towers play an important role in everyday life, not just emergency situations such as fires and thunderstorms that knock out power.
"When storms come, they can knock out electrical power pretty easily, and phone lines too, but people seldom lose their water," Mr. Supple says. "They can thank water towers for a lot of that."

For all the blinking lights and computerized monitoring that goes on in the control room at the WSSC's Laurel corporate headquarters, water tanks operate on a fairly simple concept: sheer gravity. Water builds a pound of pressure for each 2.3 feet of elevation, so to build a pressure level of 20 pounds per square inch (the minimum many major appliances require), a tank would have to be mounted 46 feet above the ground. Most tanks are mounted much higher than that to be able to supply water pressure for an entire region and for fire hydrants, which naturally require much greater water pressure.
"Water tanks kind of serve as the battery for the water-supply system," Mr. Supple says. "They're pretty simple things, actually. Just a big water supply and a couple of valves."
Water towers in this area get their water from a utility system's treatment plants after it is drawn from the Patuxent River or Potomac River and treated. Water moves from the treatment plants to customers by way of a high-pressure distribution system one with pressure so high that pumps at the water towers usually are unnecessary to force the water into the towers.
Overnight and during the day, when customer demand is down, that pressure diverts the extra water into the tanks, mostly without the need for any extra pumps or mechanical devices. When customer demand is high, such as the early morning and late afternoon, that same pressure diverts the water from the tanks back into the distribution system and to the customers. The cycle continues as the tanks refill when demand for water again is lower.
"Basically, the pressure is always there," Mr. Asner says. "It's either moving water to the customers or moving it up into the tanks."
Utility engineers monitor the filling and emptying of the tanks with sensors and computers and can regulate it if the process needs to be quickened or slowed, but for the most part, the system runs automatically.
That simplicity of design and function makes water towers a preferable backup supply over ground-level or underground reservoirs. Ground-level storage facilities are more aesthetically desirable because they are less noticeable, but they require more machinery, including switches, monitors, timers and valves, to get the job done, which means greater propensity for breakdowns.
They also rely on electrical power to get the water into the system, which means the tanks must have backup generators in case thunderstorms or other emergency situations knock out the regular power. Generators have their own set of potential problems.
Just about all of those problems are nonexistent with water towers.
"They have an altitude valve to keep them from overflowing and a check valve that regulates the water that goes back into the system, but other than that, they're pretty easy," Mr. Asner says.
"As far as maintenance goes, water towers are much more economical," Mr. Supple says. "Pipelines are very expensive. It takes a couple of million dollars to build a tank, but when you start talking about laying water pipeline, it runs much, much higher than that. If we tried to service our customers without water towers, they'd be paying probably three times as much as they are now."
Mike Marcotte, chief engineer for the D.C. Water and Sewer Authority, calls elevated water tanks "human-proof."
"They don't depend on [electrical] power," he says. "As long as the water is in the tanks, you're good to go."
Another advantage to water towers' simple technology is that they don't need frequent servicing or maintenance. Mr. Asner says the WSSC checks its towers thoroughly only about every six months, although he says many towers get visited about once a month.
"There are different levels of inspections we do," he says. "We usually get into every site once a quarter and a good mechanical check every six months, and a top-to-bottom check once a year. But we do some routine security checks about once a month."

"Our customers average about 1.6 million gallons of water a day," Mr. Supple says. "That means if you had a tank the size of a football field, that tank would have to be 370 feet high. During the summer, the demand can go as high as a quarter of a billion gallons each day. In the morning, everybody's showering and getting ready to work, so the demand tends to be at a peak. We have the tanks full and ready to go, and in the summer, we try to have a little more on hand."
Mr. Marcotte says tanks need to discharge and refill steadily to keep the water in them fresh.
"You don't want water sitting in the tanks indefinitely just waiting to be used because at that point, the water, in effect, goes bad," he says. "You try to turn the tanks over every day."
The WSSC monitors 60 water towers in Montgomery and Prince George's counties (30 in each county), ranging in size from 3 million gallons to 15 million gallons. The tanks range in height from 25 feet to 220 feet. The Fairfax County Water Authority has 19 water tanks (including the elevated ones) to service 1.2 million persons in the county. The D.C. Water and Sewer Authority maintains nine storage tanks, four of them elevated and the other five located at ground level, but on high ground throughout the city.
"A lot of people don't realize it, but parts of Washington, like Fort Reno and the National Cathedral, are up about 400 feet from sea level," Mr. Marcotte says. "We store water on high ground so if we get into a situation where we need water down at the Capitol, we can move it a fairly long distance from where it's parked to where we need it with not too much drain on the overall system."
Because water towers can be large and unsightly, utility companies try to take customers' views and preferences into account when they decide a community needs a new tower. Mr. Asner says WSSC customers are involved in just about every phase of water-tower planning, from size to location and even to color scheme. For instance, he says, the water towers at the Patuxent Wildlife Refuge in Laurel are colored green and brown to look as much as possible like large trees.
"We can do a lot of things with water towers," he says. "We can put trees around them and try to incorporate them into the community as much as possible." The WSSC's most recent water-tower project, built in Suitland in 1999, houses a 2,500-square-foot room that serves as a community center and a room for the Prince George's Community Oriented Policing Service (COPS). It earned a Tank of the Year award from the Steel Plate Fabricators Association.
Mr. Marcotte notes with a chuckle, though, that customers are never going to be completely happy with a new water tower project.
"Everybody's got a different idea of how a tower should be painted," he says. "They come up with colors we've never heard of."


Copyright © 2018 The Washington Times, LLC. Click here for reprint permission.

The Washington Times Comment Policy

The Washington Times welcomes your comments on Spot.im, our third-party provider. Please read our Comment Policy before commenting.

 

Click to Read More and View Comments

Click to Hide