Reading passage Grade 7 English Language Arts
The Hose in the Wading Pool: Backflow at Thistlewaite
A grade 7 informational passage on how a garden hose caused a cross-connection during a main repair, with comprehension questions mixing literal recall and inference.
Objectives
- Students will explain in writing how a drop in pressure can reverse the direction of water in a pipe.
- Students will cite textual evidence to support an inference about why a cross-connection is dangerous.
- Students will define cross-connection and backflow using the passage.
Vocabulary
- Backflow
- Backflow is water flowing backward through a pipe in the wrong direction, which can pull dirty water into the clean drinking water system. Special devices are installed on pipes to stop it.
- Cross-connection
- A cross-connection is any place where drinking water pipes are linked to something dirty, like a garden hose left sitting in a bucket of soapy water. If the flow reverses, the dirty water can get sucked in.
- Siphon
- A siphon is a tube that can move water uphill for a short distance and then back down, powered only by gravity and air pressure, without any pump. Once started, a siphon keeps flowing on its own as long as the outlet is lower than the water source.
- 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: pressure, vacuum breaker
Teacher overview
This passage explains backflow, a hazard most residents never hear about until a notice arrives on the door. Set in the fictional town of Thistlewaite, it follows a garden hose left in a wading pool during a water main repair and traces, step by step, how water in a pipe can reverse direction when pressure drops. The text works well before a unit on water distribution, and it gives students a clear cause-and-effect chain to gather evidence from.
Passage
Water in a town's pipes is supposed to travel one way. It leaves the treatment plant, moves through large pipes called mains under the streets, and arrives at kitchen faucets and school fountains. Pressure is what keeps it moving in that direction. Water in a system like this is usually held between 40 and 80 psi, and most state rules say it must never drop below 20 psi. That minimum is set so that water cannot travel backward through the system.
On a hot Saturday in July, a crew in the fictional town of Thistlewaite was repairing a broken main on Ash Lane. To reach the pipe, the crew had to close a valve and drain that section. For about an hour, pressure on Ash Lane fell to almost nothing. The crew posted signs and knocked on doors, which is standard for a repair of this kind.
Two blocks away, a garden hose lay coiled in a plastic wading pool. One end sat under the water. The other end was screwed tightly onto an outdoor faucet that had been left partly open. Nobody had thought about it since Thursday. The pool water had been standing in the sun for three days, and it held sunscreen, grass clippings, a little dirt, and whatever else the neighborhood children had carried in on their feet.
When the pressure on Ash Lane fell, water in the surrounding pipes began to move toward the empty section. Water always moves from higher pressure toward lower pressure. The hose became a straw. Pool water was pulled up the hose, through the faucet, into the house plumbing, and some of it reached the pipe under the street.
Plumbers and operators have a name for this setup. Any point where drinking water can meet water of unknown quality is called a cross-connection. A hose lying in a pool is a cross-connection. So is a hose attached to a sprayer full of weed killer, or a pipe that links a heating loop to a drinking line. When the flow actually reverses and the unknown water enters the drinking system, that reversal is called backflow.
Thistlewaite found out by phone. A resident on the next street called to report water that looked cloudy and smelled faintly of sunscreen. The utility sent a crew, which flushed the mains through hydrants until the water ran clear, and the town mailed a notice to every home in the area. Nobody became sick, and the sample results came back clean. The utility still treated it as a serious event, because the next cross-connection might involve something far worse than a wading pool.
The fix for a house is small and inexpensive. A vacuum breaker screws onto an outdoor faucet like an adapter. If pressure drops, a small valve inside opens to the air, which breaks the suction and stops water from climbing back up the hose. Many building codes now require one on every outside faucet.
Businesses and factories need more than that. A restaurant, a car wash, or a plant that mixes chemicals can be connected to the town system in ways that would carry far more than pool water. Those buildings must install a testable backflow preventer, a device with its own valves and test ports. A certified tester checks each device on a schedule, usually once a year, and files a report with the utility. Backflow prevention testing is a licensed trade, and many testers begin as plumbers or as water distribution operators.
Thistlewaite's crew did nothing wrong that Saturday. Dropping the pressure was necessary to fix the main. The lesson the town took from it was that the protection has to sit at the hose, not at the treatment plant, because a plant cannot clean water that enters the system downstream of it.
Questions
- According to the passage, what keeps water moving in one direction through a town's pipes?
- Why did the Thistlewaite crew have to drain the section of main on Ash Lane?
- How does the passage define a cross-connection?
- Explain how the garden hose acted like a straw during the repair. Cite at least two details from the passage.
- Nobody in Thistlewaite deliberately put anything into the town water system. Why, then, does the passage call the event serious?
- What is the purpose of the rule that pressure must never drop below 20 psi? Support your answer with evidence from the passage.
- Based on the passage, why does a restaurant need a testable device while a homeowner can use a simple vacuum breaker?
- What can you infer from the last paragraph about where the town decided protection has to be placed, and why?
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: Pressure. The passage states that pressure keeps water moving from the plant, through the mains, and out to faucets, and that systems are usually held between 40 and 80 psi.
- Answer: To repair a broken main. The crew had to close a valve and drain that section of pipe in order to reach it.
- Answer: Any point where drinking water can meet water of unknown quality. The passage gives a hose in a pool, a hose on a weed killer sprayer, and a pipe joining a heating loop to a drinking line as examples.
- Answer: Answers should cite that pressure on Ash Lane fell to almost nothing, that water moves from higher pressure toward lower pressure, and that one end of the hose sat under the pool water while the other was screwed onto a faucet left partly open. Together those details explain how pool water was pulled up the hose and into the plumbing.
- Answer: Because the same path could carry something far more harmful than pool water. The passage says the utility treated it seriously since the next cross-connection might involve something much worse.
- Answer: To keep water from going backward. The passage states that the minimum is set so that water cannot travel backward through the system, and the Ash Lane repair shows what happens when the pressure falls below it.
- Answer: Because a restaurant, car wash, or chemical plant can be connected to the system in ways that would carry far more than pool water, so its device must have test ports and be checked by a certified tester on a schedule. A homeowner's hose presents a smaller hazard, which a vacuum breaker can handle.
- Answer: Protection has to sit at the hose or the building rather than at the treatment plant, because the plant cannot clean water that enters the system after the water has already left the plant.
Differentiation
Support
Provide a simple arrow diagram showing normal flow from plant to house and reversed flow during the repair, and let students label it before answering. Allow questions 1 through 3 to be answered with a copied sentence, and let question 4 be answered orally before it is written.
Extension
Ask students to write a one-paragraph notice that Thistlewaite could mail to residents, explaining in plain language what happened, what residents should check at home, and why the crew flushed the hydrants. The notice must avoid blaming any household.
ELL supports
Pre-teach "pressure," "main," "cross-connection," "backflow," and "siphon," and demonstrate a siphon with a length of clear tubing and two cups at different heights. Provide the frame "The passage says ___, so I can infer ___" for questions 5, 7, and 8.
Extensions
Students can look at the outdoor faucets at home or at school and note whether a vacuum breaker is attached, then write a short description of what they found. A follow-up letter to the school's facilities office asking when the building's backflow preventers were last tested connects the passage to a real record students can request.