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Lesson plan Grade 5 Science

Ingleside's Midnight Meter Check: Finding a Hidden Leak

A 50-minute grade 5 lesson where students subtract 1:00 a.m. and 4:00 a.m. meter readings from two Ingleside streets to find which one hides a leak.

Objectives

  1. Students will explain how a water utility uses night meter readings to find leaks that are buried underground.
  2. Students will subtract decimal meter readings to find how much water moved through a meter overnight.
  3. Students will compare two streets' night flows and justify which one probably has a leak.

Vocabulary

Distribution system
A distribution system is the network of pipes, pumps, valves, and storage tanks that carries treated water from a treatment plant to homes, schools, and businesses. Most of it is buried underground beneath streets.
Water main
A big underground pipe that carries drinking water beneath the streets to a neighborhood. Smaller service lines branch off it to reach each building.

Also: meter, leak survey, night flow

Teacher overview

Many water leaks in a distribution system never reach the surface, so a crew cannot find them by walking around and looking for wet ground. Instead, the utility reads the meter that feeds a neighborhood in the middle of the night, when almost no one is awake to use water. Any water still moving through that meter is going somewhere it should not. In this lesson, students work with night readings from two streets in the town of Ingleside, a fictional community, and decide which street hides a leak. A common misconception in this lesson is that a leak always shows itself with a puddle or a wet spot, which leads students to expect that a crew finds a buried leak by looking for it rather than by comparing two meter readings.

Procedure

Hook (5 min): Ask students how a town could tell that water is leaking out of a pipe buried eight feet under a street. Collect two or three answers on the board without judging them. Then explain that the Ingleside crew answers the question with two meter readings taken three hours apart in the middle of the night.

Direct instruction (12 min): Read the short description of Ingleside's leak survey aloud from the handout, then project the meter table beside it so students see both sources at once. Explain that the meter counts every gallon that passes into the neighborhood, and that the number only goes up. Model one subtraction on the board using a third street that does not appear on the handout: a meter that reads 2,015.4 gallons at 1:00 a.m. and 2,021.8 gallons at 4:00 a.m. passed 6.4 gallons in those three hours. Line up the decimal points as you work, and say aloud why the later reading goes on top.

Guided practice (10 min): With partners, students find the night flow for a practice street the teacher writes on the board: 780.5 gallons at 1:00 a.m. and 792.0 gallons at 4:00 a.m., for a night flow of 11.5 gallons. Circulate and check that pairs are subtracting the earlier reading from the later one rather than the other way around. Take a quick thumbs-up poll on the answer; if fewer than two-thirds of the class has 11.5 gallons, model a second practice problem before releasing the handout.

Independent practice (15 min): Students complete the five handout questions on their own. Remind them that every question gives its own numbers, so they do not need to look back at the board.

Closure and exit check (8 min): Call on three students to defend an answer to handout question 5, then collect the handouts. Close by explaining that in the town of Ingleside, a night flow that stays high for several nights sends a crew out with listening equipment to pinpoint the break in the water main before the street washes out.

Ingleside's Midnight Meter Check: Finding a Hidden Leak — Grade 5 Science
Name: ____________________________ Date: ______________

Student Handout

Ingleside's leak survey. The Ingleside Water Department checks one neighborhood each week. A worker reads the neighborhood's big meter at 1:00 a.m. and again at 4:00 a.m. Almost nobody uses water in those hours, so the meter should barely move. When it moves a lot, water is escaping from a broken pipe underground. The department writes the readings in gallons, to the tenths place.

Street Reading at 1:00 a.m. Reading at 4:00 a.m.
Cobham Street 4,182.6 gallons 4,209.9 gallons
Barclay Court 1,536.4 gallons 1,542.1 gallons
  1. The Cobham Street meter read 4,182.6 gallons at 1:00 a.m. and 4,209.9 gallons at 4:00 a.m. How many gallons passed through that meter during those three hours?
  2. On a night with no leak, about 6.0 gallons should pass through the Cobham Street meter between 1:00 a.m. and 4:00 a.m. If 27.3 gallons passed through instead, how many extra gallons is that?
  3. The Ingleside crew found that 21.3 extra gallons pass through the Cobham Street meter every night. How many extra gallons is that in 7 nights?
  4. The Barclay Court meter read 1,536.4 gallons at 1:00 a.m. and 1,542.1 gallons at 4:00 a.m. How many gallons passed through that meter during those three hours?
  5. Cobham Street passed 27.3 gallons between 1:00 a.m. and 4:00 a.m. Barclay Court passed 5.7 gallons in the same hours. The two streets have the same number of homes. Which street probably has a hidden leak? Use both numbers in your answer.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: 27.3 gallons. Subtract the earlier reading from the later one: 4,209.9 minus 4,182.6 equals 27.3 gallons.
  2. Answer: 21.3 gallons. Subtract the expected night flow from the measured night flow: 27.3 minus 6.0 equals 21.3 gallons.
  3. Answer: 149.1 gallons. Multiply the nightly loss by the number of nights: 21.3 times 7 equals 149.1 gallons.
  4. Answer: 5.7 gallons. Subtract the earlier reading from the later one: 1,542.1 minus 1,536.4 equals 5.7 gallons.
  5. Answer: Cobham Street. Cobham Street passed 27.3 gallons while Barclay Court passed only 5.7 gallons, so about 21.6 more gallons moved under Cobham Street during hours when both streets should have been nearly still. Accept any answer that names Cobham Street and cites both night-flow numbers.

Differentiation

Support

Give these students a subtraction frame with the decimal points already lined up for questions 1 and 4, and allow a calculator for question 3. Before they begin, walk through the meter table on the Ingleside handout one row at a time and have them highlight the later reading in each row.

Extension

Ask these students to figure out how many gallons the Cobham Street leak wastes in 30 nights at 21.3 gallons per night, then write two sentences explaining why the Ingleside Water Department would rather dig up one street now than wait for the pipe to break open.

ELL supports

Pre-teach "meter," "leak," and "night flow" while pointing at the two columns of the table, and say the sentence "the meter went from 4,182.6 to 4,209.9" aloud twice. Provide the sentence starter "The street with the leak is ___ because its meter moved ___ gallons" for question 5.

Extensions

Invite students to find the water meter at their own home or school with an adult and read it before and after a two-hour stretch when no water is being used. If the reading changes, something in the building is running. Some utilities will lend a class a retired meter to take apart, which shows students that the dial is turned by the water itself.