Classroom activity Grade 10 Engineering & Design
Pikehaven Valve Isolation Drill: Shutting Down a Main Break
Grade 10 teams work a fictional distribution loop, choose the valves that isolate a broken main, and calculate the customers and gallons taken out of service.
Objectives
- Students will identify the smallest set of valves that isolates a broken segment of a looped water main.
- Students will calculate the number of service connections and the volume of water lost during an isolation.
- Students will evaluate whether adding a valve is justified by the reduction in customers affected.
Vocabulary
Key words: isolation valve, service connection, distribution main, looped system, shutdown
Teacher overview
This is a timed crew drill for teams of three or four students, set in the fictional town of Pikehaven. Each team works from a table describing a closed distribution loop of six mains and six isolation valves, and in each round the team decides which valves to close so that a broken segment can be repaired. The activity maps directly onto distribution work: closing a valve pair is the only way to take a segment out of service, so the spacing a utility chose decades earlier sets how many customers lose water today. A misconception worth naming before the drill is that a main break shuts down an entire system; in a looped network the crew closes the smallest set of valves that surrounds the break, and water keeps moving to every other segment through the rest of the loop.
Activity Directions
- Before class, print one Student Handout per team and copy the loop diagram description onto the board so the whole class can see the order of the segments and valves in the fictional Pikehaven loop. Arrange desks into team clusters of three or four.
- Setup and framing, 5 minutes. Distribute the handout and read the loop description aloud. Establish the rule that governs every round: to take a segment out of service, a crew must close the valve at each end of that segment, and any segment whose supply path is cut also loses water.
- Round 1, the clean isolation, 10 minutes. Announce that a contractor has struck Segment D. Teams answer questions 1 through 3 on the handout, working out which valve pair isolates the break, how many service connections go dry, and how much water drains from the broken main. Ask each team to highlight the closed valves on their handout before time is called.
- Round 2, the stuck valve, 10 minutes. Announce that the crew arrives at V5 and finds the valve seized, which happens often on older mains. Teams answer questions 4 through 7, extending the isolation to the next working valve and recalculating the outage and the drain time. Circulate and check that teams are adding the two segment volumes rather than doubling one of them.
- Round 3, the valve proposal, 10 minutes. Tell teams that the utility has budgeted one additional valve for the loop. Teams answer questions 8 and 9, then write a one-sentence recommendation naming the segment they would split and the reason.
- Formative check and debrief, 10 minutes. Poll the class on question 4: teams hold up a card with their number of affected connections, and if fewer than three quarters of the class has 77, work that item on the board before moving on. Close by having two teams read their valve proposals, then ask the debrief question in item 10: what does a crew give up when a utility installs valves farther apart?
Student Handout
Pikehaven is a fictional town built for this drill. Its downtown distribution system is a closed loop of six mains, labeled A through F in clockwise order. An isolation valve sits at each junction: V1 between F and A, V2 between A and B, V3 between B and C, V4 between C and D, V5 between D and E, and V6 between E and F. Every segment is fed from both directions until a valve is closed.
| Segment | Length (ft) | Inside diameter (in) | Service connections |
|---|---|---|---|
| A | 600 | 8 | 38 |
| B | 450 | 8 | 27 |
| C | 720 | 12 | 52 |
| D | 640 | 8 | 46 |
| E | 520 | 8 | 31 |
| F | 800 | 12 | 64 |
Use these relationships. Volume of a pipe in cubic feet equals 0.785 multiplied by the inside diameter in feet squared, multiplied by the length in feet. One cubic foot holds 7.48 gallons. An 8-inch pipe has an inside diameter of 0.667 feet.
A contractor breaks Segment D. Which two valves must the crew close to take only Segment D out of service?
How many service connections lose water when only Segment D is isolated?
Find the volume of water in Segment D in gallons. Segment D is 640 feet long with an inside diameter of 0.667 feet.
The crew finds V5 seized and cannot close it, so the next valve in that direction, V6, is closed instead. How many service connections lose water when Segments D and E are both out of service?
How many more service connections lose water in the stuck-valve case of question 4 than in the clean isolation of question 2?
Find the combined volume of Segments D and E in gallons. Segment E is 520 feet long with an inside diameter of 0.667 feet.
The crew drains the isolated section through a hydrant at 320 gpm. Using the combined volume from question 6, how many minutes does the drain take?
The utility budgets one new valve and installs it at the midpoint of Segment F, which splits Segment F's 64 service connections evenly between the two halves. If a break occurs on the half nearer V6, how many service connections lose water?
Compared with isolating all of Segment F, what percent reduction in affected service connections does the new valve produce?
Explain what a utility gives up when it spaces isolation valves farther apart to save money at construction time.
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: V4 and V5.
Segment D sits between the junction with C and the junction with E, so the valves at those two junctions, V4 and V5, are the pair that surrounds the break. Closing them leaves the other five segments fed through the rest of the loop.Answer: 46 service connections.
Only Segment D is out of service, and the table lists 46 service connections on Segment D.Answer: about 1,670 gallons.
Volume equals 0.785 multiplied by 0.667 squared, multiplied by 640, which is 0.785 times 0.444889 times 640, or 223.5 cubic feet. Multiplying 223.5 by 7.48 gives 1,672 gallons, which rounds to about 1,670 gallons.Answer: 77 service connections.
With V5 seized, the closed valves are V4 and V6, so Segments D and E are both out of service. Adding the table values gives 46 plus 31, or 77 service connections.Answer: 31 service connections.
The stuck valve adds all of Segment E to the outage, and 77 minus 46 equals 31 additional service connections.Answer: about 3,030 gallons.
Segment E holds 0.785 times 0.444889 times 520, or 181.6 cubic feet. Adding the 223.5 cubic feet in Segment D gives 405.1 cubic feet, and 405.1 multiplied by 7.48 equals 3,030 gallons.Answer: about 9.5 minutes.
Dividing 3,030 gallons by 320 gpm gives 9.47 minutes, which rounds to about 9.5 minutes. Accept answers between 9.4 and 9.6 minutes depending on rounding in question 6.Answer: 32 service connections.
The new valve splits Segment F's 64 service connections evenly, so each half carries 64 divided by 2, or 32 service connections, and only one half is isolated.Answer: 50 percent.
The outage falls from 64 service connections to 32, so the reduction is 32 divided by 64, which is 0.50, or 50 percent.Answer: A wider valve spacing means a larger outage for every repair.
Accept any answer explaining that fewer valves lower construction cost but lengthen the section that must be closed, so more customers lose water, more water is drained and wasted, and the repair takes longer to refill and disinfect. Strong answers also note that a seized valve pushes the isolation out to the next valve, which makes wide spacing worse when equipment fails.
Differentiation
Support
Give these teams a completed Round 1 as a worked example, with the valve pair circled and the volume calculation shown line by line, so their independent work begins at Round 2. Pre-fill the diameter conversion for them and let them use the segment table as a checklist, crossing off each segment as they decide whether it still has water.
Extension
Ask these teams to rank all six segments by the number of customers a break would affect, then argue for the single valve placement that lowers the worst-case outage by the largest amount. Require the argument to name both the customers protected and the segment volume that would no longer be drained.
ELL supports
Post a labeled word bank with the terms isolation valve, service connection, main, loop, and drain, each paired with a simple sketch. Pair students so that every team has one member who can restate the closure rule in the student's home language, and allow answers to question 10 to be given orally or as a labeled diagram rather than in writing.
Extensions
Run a fourth round in which two breaks occur at once, on Segments B and E, and ask teams to find the valve set that keeps the largest number of customers in service. Teams can also research how their local utility labels valves in the field, using a public valve map or a utility exercise report if one is available, and compare that spacing with the fictional Pikehaven loop.