Iowa Public Television

Challenge Question Number 1 for Leak Surveyor #1073

Clearly describe what you expect from the students:
Students will be able to plan the sequence of steps necessary for solving the problem of locating the leak. They will work through the same problem-solving steps Water Works employees do by formulating questions and finding out their answers as listed in the teacher guidance section below.
Note: Probably the best approach toward making this challenge meaningful to students would be for the teacher to serve as the resource for answering the series of questions posed by students (answers in parentheses), so they can work through the problem together in a logical manner.

In order to give the teacher some guidance in evaluating the student's project(s); list some tips that may help to assess the student's work:
Helpful background information (to be shared with students):
The Water Works is responsible for upkeep and repair of all water mains in the metropolitan area and several other outlying areas, but is not responsible for water mains in most of the suburbs, even though they supply water to these communities. The individual communities provide their own crews for leak detection and local main repairs.

Water mains are usually located in the "right of way" throughout the city; that is, they lie under streets, sidewalks, parking areas, and the grassy areas between the sidewalk and the street. The Water Works has maps that display all of the water mains and their sizes, hydrants, valves, joints, bends or reducers (change to smaller pipes) in our service area.
Leading out from water mains are "service lines" that transfer water from the mains to individual homes and businesses. These lines are owned by individual property owners who are responsible for making repairs to these lines if they leak.
The Customer Service representatives at Water Works take calls from area residents and transfer these types of calls to the dispatcher to alert a leak locate technician to go out to the area and determine where the leak is and its extent.
Working through the problem- A scenario requiring teacher guidance:
1.What information would the dispatcher need to find out before she/he dispatches a leak locate technician? What is the resident's address? Is this home located in the Water Works service area?(yes) How long has the person's water pressure been low?(several hours) Is the water pressure low all through the house or just from one faucet?(all through the house. Has she seen water leaking into the street or anywhere else?(no) Has the stopbox [box where water to a customer can be turned on or off at the street] been operated lately?)(no)
2.What might the dispatcher suspect since only one resident has called in from that area with a water pressure problem? (the leak may be in her service line and not the water main since no one else is experiencing a problem) What will the dispatcher do next? (call a Water Works leak locate technician to check out the situation)
3.Shortly after hanging up the phone, the dispatcher receives calls from two people who live in the same area telling of water leaking into the street. What will the dispatcher do?(call the technician to alert to new information)
4.Besides the information already gathered by the dispatcher in the first question, what other information do you think the leak locate technician will request before going out on the call? [a map of the area (residential area), location and size of valves in the area that may need to be shut off to stop water flowing through the main (one at each corner of the block), the size of the water main (8"), any previous leak information pertaining to that area, (no previous main breaks in the area and no area stopboxes have been turned on or off lately), how long the water has been flowing into the street (just started)]
5.A leak locate technician has special equipment for pinpointing the leak. What do you think this equipment consists of? [a leak locate technician is going to make use of sound waves to locate the leak, so the special equipment consists of a Metro-Tech (a transmitter and receiver device used to locate underground mains by sending a signal into the pipe),an electronic correlator (a computer that analyzes main break sound data that it receives from two transmitter/receivers that receive sound waves and transmit the data to the correlator), an electronic sounding device with headphones, a t-shaped metal probe rod, a hammer drill, and a measuring wheel]
6.How do you think the technician will use the correlator? [after finding the main with the Metro-Tech and measuring the distance between two valves on either side of the suspected leak with the measuring wheel (100 ft.), he will attach a transmitter/receiver to each valve (or could use hydrants) to start tracking down a more precise location with the correlator]
7.The correlator shows that a leak is located 80 feet from one valve and 20 from the other.The technician now will measure to the location indicated by the correlator.To verify the exact location of the leak, he will then use a hammer drill, the t-shaped metal probe rod, and the electronic sounding device with headphones. How do you think each piece of equipment will be used?[drill into the street or ground (usually about 18"), then try to hit the main with a long probe rod (water mains are usually 4-6 feet below the surface), once the probe is in contact with the water main, set the electronic sounding device with headphones on top of the metal probe to listen to leak sounds via its headphones]
8.For further accuracy in pinpointing the leak, he will drill at least two more holes, one on either side of the first hole, several feet away, to listen for where the loudest sound is occurring. If he detects the loudest and highest-pitched sound at the probe rod where the correlator indicated the leak was, then he has located the leak. What do you think he will do next? (call a crew from Water Works to repair or replace that section of water main)
9.Before the crew can begin to dig to repair, Iowa-One-Call must be contacted for emergency locators. Iowa-One-Call puts a call out to all area parties that may have something underground that could be hit/damaged while digging. What are some underground utilities that could be hit that Water Works must be aware of? (private service lines (taps), sewer lines, gas lines, phone lines, electrical lines to traffic lights, electrical lines to RR crossings, fiber optic lines, other electrical lines)
10.The leak locate technician will mark locations for the repair crew. What do you think he will mark? (the leak location, the main location, taps to any nearby service lines)
11.Ask students what they think are the major causes of water main leaks. [corrosion of cast iron pipes over time by the natural acidity of soil; ground temperature variations putting stress on pipes, for example, frost and thawing; construction workers hitting mains; changes in water pressure during periods of high then lower usage; changes in the temperature of the water flowing through the main (expansion/contraction]