Classroom activity Grade 3 Science

Northwick's Broken Water Main: A Grade 3 Valve Map Activity

A 50-minute grade 3 activity where crews rotate through four repair stations and use a made-up valve map to shut off the fewest houses while fixing a leak.

Grade: Grade 3
Subject: Science
Material: Classroom activity
Time: 50 min
Prep: Low prep
Materials: A printed valve map for each crew, Four station signs, Four role cards per crew, Two paper towel tubes for listening sticks, A tray of sand and two plastic pipe pieces for the dig station, A spare pipe piece, a cup of clean water, and an empty cup for station four, Paper sample tags and one water-back-on card per crew, A timer, A printed copy of the handout for each student

Standards

3-5-ETS1-1 NGSS

Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost.

How this material aligns: Handout items 5 and 6 state the crew's goal of shutting off the fewest houses and the two-hour limit the repair has to fit inside.

All materials for 3-5-ETS1-1 →

3.NBT.A.2 Common Core Math

Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.

How this material aligns: Handout items 1 through 4 add four two-digit house counts to 100 and subtract to compare how many homes each valve choice shuts off.

All materials for 3.NBT.A.2 →

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This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-09-04.

Objectives

Students will read a valve map to decide which valves close off a broken pipe.
Students will add and subtract house counts to compare two shutoff choices.
Students will name the steps a crew takes before water is used again.

Vocabulary

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.
Valve: A valve is a device in a pipe that operators can open or close to control where water flows. Valves let crews shut off one street for repairs without turning off the whole town.

Also: leak, crew, flush, sample

Teacher overview

This is a four-station rotation for crews of four, built around a single decision a real repair crew makes within minutes of finding a leak: which valves to close, given that every valve turned shuts water off for somebody. Each station stands for one step of the repair in the order it happens, so crews physically move from finding the leak, to choosing valves on a map, to replacing the pipe, to flushing and sampling before anyone drinks. The arithmetic takes place at the map at station two, since the crew has to compare the house counts behind two different shutoff choices. The rotation ends when every crew has posted its water-back-on card, and a short debrief closes the lesson.

Activity Directions

Set up (6 min). Post the four station signs around the room in order. Put the listening tubes at station one, the valve maps and handouts at station two, the sand tray and pipe piece at station three, and a cup of clean water and a paper sample tag at station four. Sort students into crews of four and hand out role cards for locator, valve turner, digger, and sampler.
Brief the crews (5 min). Tell the class that a water main under Mill Street in the made-up town of Northwick started leaking this morning. State the crew's goal aloud: stop the leak and keep water on for as many houses as possible. State the limit aloud: the repair must be done in two hours, before school lets out.
Station 1, find the leak (8 min). The locator holds a paper tube to a table leg while a partner taps the far end, then reports where the sound is loudest. Crews mark the leak spot on their map between Valve 2 and Valve 3.
Station 2, choose the valves (12 min). Crews study the valve map and the house counts, then answer handout items 1 through 6 together. The valve turner announces the crew's choice to the teacher before the crew moves on.
Station 3, replace the pipe (10 min). The digger uncovers the plastic pipe piece buried in the sand tray, swaps it for a clean piece, and covers it again. Crews time this step and compare it with the two-hour limit.
Station 4, flush and sample (6 min). The sampler pours clean water through the new pipe piece into a cup, fills out the paper sample tag, and posts the crew's water-back-on card on the board. No one drinks the water at this station. The rotation ends when all crews have posted a card.
Debrief (3 min). Ask two questions with the maps still out: which valve choice would have shut off the whole town, and why does a crew flush the pipe before anyone drinks from it?

Northwick's Broken Water Main: A Grade 3 Valve Map Activity — Grade 3 Science

Name: ____________________________ Date: ______________

Student Handout

Northwick is a made-up town. Its water main runs under Mill Street. Four blocks branch off the main. Three valves sit on the main pipe.

Valve 1 sits at the tower end. It shuts off all four blocks at once. Past Valve 1, the main makes a loop. Block A gets water from one side of the loop, and Block D gets water from the other side. Valve 2 sits between Block A and Block B. Valve 3 sits between Block C and Block D. Closing Valve 2 and Valve 3 together shuts off Block B and Block C only.

The leak is in the pipe between Valve 2 and Valve 3.

Block	Houses
Block A	18
Block B	26
Block C	34
Block D	22

Block A has 18 houses. Block B has 26 houses. Block C has 34 houses. Block D has 22 houses. How many houses is that in all?
Closing Valve 1 shuts off all four blocks. How many houses lose water?
Closing Valve 2 and Valve 3 shuts off Block B and Block C only. How many houses lose water?
Closing Valve 1 shuts off 100 houses. Closing Valve 2 and Valve 3 shuts off 60 houses. How many more houses lose water with Valve 1?
The crew wants to stop the leak and keep water on for as many houses as it can. Which valves should the crew close?
The crew has only two hours before school lets out. Is that a goal or a limit? Tell why.
Name one thing the crew must do after the new pipe is in, before people drink the water.

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

Answer Key

Answer: 100 houses. 18 plus 26 is 44, 44 plus 34 is 78, and 78 plus 22 is 100.
Answer: 100 houses. Valve 1 shuts off all four blocks, and the four blocks hold 100 houses in all.
Answer: 60 houses. Block B has 26 houses and Block C has 34 houses, and 26 plus 34 is 60.
Answer: 40 houses. 100 minus 60 is 40.
Answer: Valve 2 and Valve 3. Closing those two valves shuts the water off around the leak and leaves Block A and Block D with water, so 40 fewer houses go dry.
Answer: A limit. Accept any answer explaining that the two hours is a boundary the crew cannot change, while a goal is what the crew is trying to achieve, which here is stopping the leak with the fewest houses shut off.
Answer: Flush the pipe. Accept any answer naming flushing the line, taking a water sample, or waiting for the sample result before people drink, since dirt and germs can get into an open pipe during the repair.

Differentiation

Support

Give these students a valve map with Block B and Block C already shaded so the leak section is obvious, and a place-value chart for item 1. Let them build the house totals with base-ten blocks before writing. Pair them with a partner who reads each handout item aloud, and let items 5 and 6 be answered by pointing to a labeled choice box.

Extension

Ask these students to add a fourth valve to the made-up map, place it where it would shut off the fewest houses of all for this leak, and write the new house count. Have them explain what the town would have to pay for to gain that smaller shutoff, and whether they think it is worth it for a street with 100 houses.

ELL supports

Pre-teach "valve," "main," and "leak" with a length of hose and a clamp that stops the flow. Post the map with picture labels for the tower, the valves, and the blocks. Provide the frames "Closing Valve ___ shuts off ___ houses" and "This is a ___ because ___," and allow item 7 to be answered by holding up the flush card or the sample tag.

Extensions

Ask a local utility whether it will share a simple map of the valves near the school, or use a public system map if one is posted online, and have students compare its layout with the made-up Northwick map. Students can then write one sentence about how many valves sit between the school and the nearest tower.