WASHINGTON, D.C. — A leaky pipe can cause a lot of damage. In a home, it can ruin floors, walls and furniture. Outdoors, water leaking from a high-pressure water pipe can wash away soil and create sinkholes. And even before such leaks cause damage, they can rob communities of massive amounts of clean water needed for drinking and other uses. But a teen now reports a way to detect damage in a water pipe — even one buried in the ground. In some cases, his technique might find a failing pipe before it leaks a drop.
Sanjay Seshan, 15, attends Dorseyville Middle School in Pittsburgh, Pa. He presented his research here, October 21, at the finals of the Broadcom MASTERS science competition. (MASTERS stands for Math, Applied Science, Technology and Engineering for Rising Stars.) This event brings together 30 middle-school finalists each year for a special competition. Society for Science & the Public, which publishes Science News for Students, created the program in 2011. The Broadcom Foundation of Irvine, Calif., sponsors the event.
“Water leak” may bring to mind the slow drip, drip, drip of a bathroom faucet. Yet some leaks can be huge. And if there are enough of them, even small leaks can add up to massive losses, notes Sanjay. He first became aware of large-scale water leaks while traveling through a poor area in India. There, he recalls seeing just “one community pipe and leaking water everywhere.” When he returned home, Sanjay did some research. He learned that the U.S. water-delivery infrastructure is deteriorating, too. (Infrastructure is a term for the basic physical structures and facilities on which a society depends. These include roads, bridges, sewer systems, electrical power grids and phone systems.)
That deteriorating water infrastructure includes an estimated 240,000 breaks each year in water mains. These are the pipes that run water from treatment plants to neighborhoods. Overall, he learned, U.S. water-delivery systems lose some 7.6 trillion liters (2 trillion gallons) of water annually. That’s equal to the water needed to fill some 25 billion bathtubs. It’s also enough to provide every person on Earth about 1,000 liters (270 gallons) of water each year. Across North America today, Sanjay reports, about one liter (or quart) out of every 6.5 liters fed into water-distribution pipes simply disappears due to leaks. That a huge waste of money and clean water.
In poorer nations, the problem can be much worse. A 2004 report by the Asian Development Bank reports that the pipes in Delhi, India, lose a little more than half of all clean drinking water to leaks. In Dar es Salaam, a major city in the East African nation of Tanzania, about 60 percent of the city’s water disappears through broken pipes. That’s according to a 2003 report by the United Kingdom’s Department for International Development. In the many parts of the world where clean water is scarce, any loss is a big deal. But losses this high can sometimes prove tragic.
Such data motivated Sanjay to explore how he might scout for damage in buried water pipes. Finding a failing pipe before leaks become big and obvious would save a lot of water, he notes. An out-of-tune clarinet provided his inspiration.
A clarinet is essentially a long tube with holes that a player opens and closes to change the sounds coming out of the instrument. If a clarinet becomes damaged, those sounds will be slightly off. Sanjay figured that the way sound travels through a water pipe, another long tube, should change if the pipe becomes damaged. The teen then designed a way to test that. (And his parents were good sports, because some of his experiments involved digging up large parts of their backyard.)
Sanjay used lengths of pipe made from a type of plastic known as polyvinyl chloride, or PVC. He attached a tiny but powerful speaker to the outside of a pipe. He also attached two small microphones to the pipe. He put one near the speaker and another much farther away. Then, he used a computer program to send electrical signals to the speaker.
Those signals caused the speaker to vibrate at particular frequencies. A sound’s pitch is due to the frequency at which its sound waves vibrate. The lowest pitch he tested was 1000 hertz (cycles per second). He also tried six other frequencies, ranging from 2,000 to 20,000 hertz. In each case, he compared the size of the vibrations picked up by each of the two tiny microphones. He showed that the pipe transmitted some frequencies better than others. (This science of sound falls into a field known as acoustics.)
After measuring how well a healthy pipe transmitted each sound pitch, Sanjay damaged the pipe. In some cases, he drilled small holes. For other tests, he used a tool to scratch the pipe. (Those scratches were sometimes so shallow that they never would have caused the pipe to leak.) Then, Sanjay ran his tests again. The pipe’s sound transmission changed. This was true even for pipes 3 meters (about 10 feet) long that he’d buried in his backyard. So, he concludes, the technique offers hope that pipes could be rigged with sensors and then monitored over long periods.
There is one small issue, though. Sanjay notes that the technique only works when there are original measurements of sound transmission available from before a pipe is damaged. They will provide a value against which future measurements can be compared. While it would be possible to make measurements on pipes that have been in use a long time, engineers could only confidently measure damage that occurs in the future. The technique could not gauge how much had taken place in the past.
Still, says Sanjay, the technique might work on more than just buried pipes. Studies have suggested that bridges might vibrate differently if some of their parts have cracked.
acoustic Having to do with sound or hearing.
Broadcom MASTERS Created and run by the Society for Science & the Public in 2011, Broadcom MASTERS (Math, Applied Science, Technology and Engineering Rising Stars) is the premier middle school science and engineering fair competition. Broadcom MASTERS International gives select middle school students from around the world a unique opportunity to attend the Intel International Science & Engineering Fair.
computer program A set of instructions that a computer uses to perform some analysis or computation. The writing of these instructions is known as computer programming.
engineer A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.
frequency The number of times a specified periodic phenomenon occurs within a specified time interval. (In physics) The number of wavelengths that occurs over a particular interval of time.
gauge A device to measure the size or volume of something. For instance, tide gauges track the ever-changing height of coastal water levels throughout the day. Or any system or event that can be used to estimate the size or magnitude of something else. (v. to gauge) The act of measuring or estimating the size of something.
grid (in electricity) The interconnected system of electricity lines that transport electrical power over long distances. In North America, this grid connects electrical generating stations and local communities throughout most of the continent.
hertz The frequency with which something (such as a wavelength) occurs, measured in the number of times the cycle repeats during each second of time.
middle school A designation for grades six through eight in the U.S. educational system. It comes immediately prior to high school. Some school systems break their age groups slightly different, including sixth grade as part of elementary school and then referring to grades seven and eight as “junior” high school.
pitch (in acoustics) The word musicians use for sound frequency. It describes how high or low a sound is, which will be determined by the vibrations that created that sound.
plastic Any of a series of materials that are easily deformable; or synthetic materials that have been made from polymers (long strings of some building-block molecule) that tend to be lightweight, inexpensive and resistant to degradation.
polyvinyl chloride (PVC) This is a plastic formed by using heat to turn a liquid resin into a solid. The plastic can be soft and flexible or rigid and hard. The raw ingredients consist primarily of chlorine and carbon.
pressure Force applied uniformly over a surface, measured as force per unit of area.
sensor A device that picks up information on physical or chemical conditions — such as temperature, barometric pressure, salinity, humidity, pH, light intensity or radiation — and stores or broadcasts that information. Scientists and engineers often rely on sensors to inform them of conditions that may change over time or that exist far from where a researcher can measure them directly.
sewer A system of water pipes, usually running underground, to move sewage (primarily urine and feces) and storm water for collection — and often treatment — elsewhere.
sinkhole A body of water that forms when a patch of ground opens up, revealing a rocky cavern below. That rocky structure then accumulates rainwater because there no opening below that allows the water to easily exit.
sound wave A wave that transmits sound. Sound waves have alternating swaths of high and low pressure.
transmission Something that is conveyed or sent along. (in mechanics) In a liquid-fueled vehicle, the machinery used to transfer power from the engine to the drive wheels. (In medicine) To spread a disease or toxic agent.
trillion A number representing a million million — or 1,000,000,000,000 — of something.
tune (in engineering) Adjust to the right level.
vibrate To rhythmically shake or to move continuously and rapidly back and forth.
waste Any materials that are left over from biological or other systems that have no value, so they can be disposed of as trash or recycled for some new use.
water main The primary pipe bringing drinking water to areas within an urban neighborhood. It is usually buried at least a meter (roughly 3 feet) below city streets.
wave A disturbance or variation that travels through space and matter in a regular, oscillating fashion.