Water for Schools
Menu

Worksheet Grade 8 Science

Lead Service Lines in Ellsworth: Corrosion Control and Limits

A grade 8 science worksheet on lead in drinking water: students weigh corrosion control, compare tap results to the shifting action level, and use scientific notation.

Objectives

  1. Students will explain how corrosion control reduces lead in tap water where lead pipes remain, and why the pipes are still replaced.
  2. Students will compare measured tap-water lead levels to the current and future federal action levels.
  3. Students will write lead-service-line counts in scientific notation and compare their magnitudes.

Vocabulary

Service line
A service line is the small pipe that connects the water main under the street to the plumbing inside one home or building. It is the last leg of the trip water makes to your tap.
Corrosion control
Treatment that keeps water from slowly eating away at the inside of pipes. It helps stop metals like lead from getting into drinking water.
Action level
A trigger number in lead and copper testing. If too many homes test above this level, the utility must take steps like improving treatment and telling the public.

Also: parts per billion, scientific notation

Teacher overview

Lead pipes are common in older water systems, and how much lead reaches the tap depends heavily on treatment. Treatment plants use a step called corrosion control that coats the inside of old pipes with a thin protective layer, greatly reducing how much lead dissolves into the water. This worksheet uses the fictional Ellsworth water system to help students see how corrosion control, tap sampling, and a tightening federal action level work together. A common misconception is that corrosion control makes a lead pipe safe for good; in practice, corrosion control greatly reduces how much lead reaches the tap, while replacing the lead line is the permanent fix.

Lead Service Lines in Ellsworth: Corrosion Control and Limits — Grade 8 Science
Name: ____________________________ Date: ______________

Student Worksheet

Use the following information about the fictional Ellsworth water system for every item.

Ellsworth has 8,000 service lines, the short pipes that connect each home to the water main. Of those, 1,200 are made of lead, 600 are galvanized steel scheduled for replacement, and 6,200 are copper or plastic. Ellsworth's treatment plant adds orthophosphate, a corrosion-control chemical that coats the inside of the pipes. Federal rules set a lead action level of 15 ppb (parts per billion) today, dropping to 10 ppb in 2027. A utility exceeds the action level when more than 1 in 10 of its samples are above it, and homes with high results get follow-up testing. The rules also require utilities to replace nearly all lead service lines within about 10 years. Nationally, EPA estimates that about 4,000,000 lead service lines remain. Ellsworth sampled tap water at four homes and measured lead levels of 4 ppb at House 1, 18 ppb at House 2, 11 ppb at House 3, and 22 ppb at House 4.

  1. In your own words, what is a service line?
  2. Ellsworth adds orthophosphate to coat the inside of its pipes. Explain how this corrosion control reduces the lead in tap water even though 1,200 lead lines are still in the ground.
  3. Explain how corrosion control lowers the risk from a lead service line, and why the line is still scheduled for replacement.
  4. Ellsworth has 8,000 service lines, and 1,200 of them are lead. What percent of Ellsworth's service lines are lead?
  5. Write Ellsworth's 1,200 lead service lines in scientific notation.
  6. Nationally, about 4,000,000 lead service lines remain. Write that number in scientific notation.
  7. Using your answers to items 5 and 6, about how many times more lead service lines are there nationally than in Ellsworth?
  8. The current action level is 15 ppb. Which of Ellsworth's four sampled homes are at or above 15 ppb?
  9. The action level drops to 10 ppb in 2027. Which sampled home is at or above 10 ppb but still below the current 15 ppb level?
  10. Ellsworth must replace its 1,200 lead service lines over about 10 years. If it replaces the same number each year, how many lead lines must it replace per year?
  11. Explain why lowering the action level from 15 ppb to 10 ppb could flag more Ellsworth homes for follow-up, using the four sample results as your evidence.

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: The pipe that connects one home to the water main.
    A service line is the short section of pipe running from the public water main to an individual house; when it is made of lead, it is a possible source of lead in that home's tap water.
  2. Answer: It coats the pipe so much less lead can dissolve into the water.
    Orthophosphate builds a thin mineral layer on the inside wall of each pipe, and that layer separates the flowing water from the lead metal, so far less lead leaches into the water.
  3. Answer: Working corrosion control keeps most of the lead in the pipe wall.
    As long as the protective coating stays intact, very little lead reaches the water, which lowers the risk; the coating cannot guarantee zero lead, and EPA's health goal for lead is zero, which is why lead lines are still being replaced. The danger rises when treatment is skipped or changed and the coating breaks down.
  4. Answer: 15 percent.
    1,200 lead lines ÷ 8,000 total lines × 100 = 0.15 × 100 = 15 percent.
  5. Answer: 1.2 × 10^3.
    1,200 = 1.2 × 1,000 = 1.2 × 10^3 lead service lines.
  6. Answer: 4 × 10^6.
    4,000,000 = 4 × 1,000,000 = 4 × 10^6 lead service lines.
  7. Answer: About 3,300 times.
    (4 × 10^6) ÷ (1.2 × 10^3) = (4 ÷ 1.2) × 10^3 ≈ 3.3 × 10^3, and 4,000,000 ÷ 1,200 ≈ 3,333, so the nation has about 3,300 times as many lead service lines as Ellsworth. Accept answers from about 3,300 to 3,333.
  8. Answer: House 2 and House 4.
    House 2 measured 18 ppb and House 4 measured 22 ppb; both are at or above the current 15 ppb action level. House 1 (4 ppb) and House 3 (11 ppb) are below it.
  9. Answer: House 3.
    House 3 measured 11 ppb, which is at or above the future 10 ppb level but still below the current 15 ppb level.
  10. Answer: 120 lines per year.
    1,200 lead lines ÷ 10 years = 120 lead service lines replaced each year.
  11. Answer: More homes cross the lower action level.
    At 15 ppb, only House 2 and House 4 would be flagged for follow-up. Lowering the action level to 10 ppb adds House 3 (11 ppb), so a stricter standard catches homes whose lead levels sit between 10 and 15 ppb.

Differentiation

Support (below grade level)

Provide a number line marked at 10 and 15 ppb and have students plot the four home results on it before answering items 8 and 9, so the comparisons are visual. Give the percent formula from item 4 already set up as 1,200 ÷ 8,000 for students to finish.

Extension (above grade level)

Ask students to calculate how many years Ellsworth's replacement program would take if it could only afford to replace 80 lead lines per year instead of 120, and to explain what that slower pace would mean for the federal 10-year requirement.

ELL supports

Pre-teach "service line," "corrosion control," and "action level" with a labeled diagram of a house, a water main, and the pipe between them. Allow students to answer items 8 and 9 by circling home numbers on the number line from the Support note instead of writing sentences.

Extensions

Have students explain, using only the numbers in this worksheet, why a utility builds a service-line inventory (a map of which pipes are lead) before it starts replacement, and why the homes that tested highest might be replaced first.