Worksheet Grade 7 Science

Brackenfell Ridge Pressure Zones: From Elevation to psi

Students use the 0.433 psi per foot constant to turn house elevations in a fictional hill town into water pressures, then judge which homes fall outside safe limits.

Grade: Grade 7
Subject: Science
Material: Worksheet
Time: 40 min
Prep: No prep
Materials: Calculator

Standards

7.RP.A.2 Common Core Math

Recognize and represent proportional relationships between quantities, including identifying the constant of proportionality and representing proportional relationships by equations.

How this material aligns: Item 9 asks students to name 0.433 psi per foot as the constant of proportionality linking head and pressure, after items 1 through 8 use it.

All materials for 7.RP.A.2 →

MS-ETS1-1 NGSS

Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.

How this material aligns: Item 14 has students state two criteria and one constraint for siting a second tank, using the pressure limits and elevations from this worksheet.

All materials for MS-ETS1-1 →

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This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-07-23.

Objectives

Students will calculate head in feet from a tank elevation and a house elevation.
Students will convert feet of head to pressure in psi and back again.
Students will state criteria and constraints for the location of a new water tank.

Vocabulary

Pressure zone: A pressure zone is a section of a water system that a utility manages separately because it sits at a different elevation than the rest of the town. Utilities create pressure zones so that water pressure stays safe and steady for everyone, whether they live at the bottom of a hill or near the top.
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.

Also: head, elevation, psi

Teacher overview

Water pressure in a town's pipes comes mostly from height. Every foot of water standing above a tap pushes down with 0.433 psi, so a house far below the tank feels more pressure than a house near the top of the hill. Utilities keep most homes between 40 and 80 psi, and most states require at least 20 psi everywhere so that outside water cannot get pulled into a pipe. This worksheet uses the fictional town of Brackenfell, where one tank serves houses at four different elevations. Teaching note: students often think pressure depends on the width of the pipe or on how much water the tank holds. The height of the water surface above the tap is what sets the pressure, so a small tank placed high on a ridge can deliver more pressure than a much larger tank sitting in a valley.

Brackenfell Ridge Pressure Zones: From Elevation to psi — Grade 7 Science

Name: ____________________________ Date: ______________

Student Worksheet

The town of Brackenfell sits on a hillside. Its one tank stands on the ridge, and the water surface inside the tank sits at an elevation of 900 feet. Four houses take water from the same tank.

House	Ground elevation (feet)
House A	700
House B	780
House C	855
House D	820

Head is the height of the tank's water surface above a house, measured in feet. Pressure in psi equals head in feet times 0.433. To go the other way, feet of head equals psi times 2.31.

How many feet of head does House B have? Subtract its elevation from the tank's 900 feet.
What is the water pressure at House B in psi? Round to the nearest tenth.
What is the water pressure at House A in psi? Round to the nearest tenth.
Brackenfell tries to keep homes between 40 and 80 psi. Is House A inside that range, above it, or below it?
How many feet of head does House C have?
What is the water pressure at House C in psi? Round to the nearest tenth.
Most states require at least 20 psi at every tap. Does House C meet that minimum?
What is the water pressure at House D in psi? Round to the nearest tenth.
Head in feet and pressure in psi form a proportional relationship. What is the constant of proportionality, in psi per foot?
A crew reads 65 psi on a gauge at a fire hydrant in Brackenfell. How many feet of head is that? Round to the nearest whole foot.
Brackenfell wants House C to have at least 40 psi. How many feet of head does House C need?
House C sits at 855 feet. Using your answer to item 11, how much higher than 900 feet would the tank's water surface have to sit?
House C is closer to the tank than House A is, yet House C has the weaker pressure. Explain why.
Brackenfell plans a second tank for houses even higher on the ridge. Write two criteria the new tank must meet and one constraint the town has to work within.

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: 120 feet.
900 feet minus 780 feet equals 120 feet of head.
Answer: 52.0 psi.
120 feet times 0.433 psi per foot equals 51.96 psi, which rounds to 52.0 psi.
Answer: 86.6 psi.
900 feet minus 700 feet equals 200 feet of head, and 200 times 0.433 equals 86.6 psi.
Answer: Above the range.
86.6 psi is greater than 80 psi, so House A sits above the range Brackenfell aims for and would likely need a pressure reducing valve.
Answer: 45 feet.
900 feet minus 855 feet equals 45 feet of head.
Answer: 19.5 psi.
45 feet times 0.433 equals 19.485 psi, which rounds to 19.5 psi.
Answer: No.
19.5 psi is below the 20 psi minimum, so House C would not meet the requirement during normal use.
Answer: 34.6 psi.
900 feet minus 820 feet equals 80 feet of head, and 80 times 0.433 equals 34.64 psi, which rounds to 34.6 psi.
Answer: 0.433 psi per foot.
Each additional foot of head adds the same 0.433 psi, so that value is the constant of proportionality.
Answer: 150 feet.
65 psi times 2.31 feet per psi equals 150.15 feet, which rounds to 150 feet.
Answer: 92.4 feet.
40 psi times 2.31 feet per psi equals 92.4 feet of head.
Answer: 47.4 feet.
House C needs a water surface at 855 plus 92.4, which is 947.4 feet. That is 947.4 minus 900, or 47.4 feet higher than the tank's surface today.
Answer: House C sits higher on the hill.
Pressure depends on how far the water surface is above the tap, not on the distance along the pipe. House C has only 45 feet of head, while House A has 200 feet.
Answer: Accept any two workable criteria and one real constraint.
Sample criteria: the tank must give every house it serves at least 20 psi, and it must keep those houses under 80 psi. Sample constraints: the town owns only one parcel high enough on the ridge, or the budget covers a tank of a fixed size.

Differentiation

Support

Give students a side-view sketch of the Brackenfell hillside with the tank, the four houses, and the head for House B already drawn as a labeled arrow. Work item 2 with the class, then let students repeat the same two steps for the other houses.

Extension

Ask students to find the elevation at which a Brackenfell house would read exactly 40 psi, then explain in writing why every house above that line needs either a second tank or a booster pump.

ELL supports

Provide a two-column word bank pairing head with height of water above the house and psi with pressure. Allow students to answer item 13 by labeling a diagram of the town of Brackenfell instead of writing a paragraph.

Extensions

Have students measure the elevation difference between their school and the nearest water tower using an online contour map, then estimate the pressure that difference would produce and compare it with the Brackenfell results.