Clearwell

Water Treatment Grade 1 exam prep that shows its source

Clearwell has 172 practice questions for the Water Treatment Grade 1 operator exam. Every answer comes with an explanation and the public source it rests on, so you can check it yourself. It works offline, with no account.

Clearwell is not a government app. It is an independent study aid made by 8086 LLC, not affiliated with or endorsed by the EPA, OSHA, any state agency, exam board or licensing agency. Its questions are written from the public sources listed below.

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Free to download, with the first 3 questions of every mode. One $12.99 purchase unlocks all 172. No subscription.

Three things you can check

Every answer cites its source

Open any explanation: the citation, the source's own words and a link to read it at the source are there, for all 172 questions.

One price, once

A single $12.99 one-time unlock, with no subscription. The best-known paid app charges $29.99–$49.99 for 6–12 months of access.

Nothing leaves your phone

No account, no sign-in, no tracking. Your scores, streak and missed questions stay on your device, and the app runs in airplane mode.

See it in the app

Four study modes, one $12.99 unlock
A revealed answer marked Correct, with its explanation, the line Source: 40 CFR 141.2, definition of coagulation (EPA), the regulation's own words, and a Read it at the source link.
Every answer shows its public source
Score, pass mark and streak, on your device

Built for water treatment operators

  • 172 original questions across 12 topics, from treatment math and disinfection to cross-connections and lead and copper
  • Four study modes: Quick 10, Timed Quiz (20 questions), Past-Errors Review and Full Mock Exam (100 questions, 70% to pass)
  • Nothing is removed: every question you answer stays reachable in All Questions
  • For iPhone and iPad (iOS 26 and later) and Android (Android 10 and later), with dark mode, large text and screen readers

Privacy in one line: Clearwell collects no data at all; your progress stays on your device. Read the privacy policy.

Sources

Every question cites one of these public sources, and the app links each one.

  1. Code of Federal Regulations, Title 40, Parts 136–149, revised as of July 1, 2025 (Office of the Federal Register / GPO; rules issued by U.S. EPA) — https://www.govinfo.gov/bulkdata/CFR/2025/title-40/CFR-2025-title40-vol25.xml
  2. Code of Federal Regulations, Title 29, Parts 1900–1910.999, revised as of July 1, 2025 (Office of the Federal Register / GPO; rules issued by OSHA) — https://www.govinfo.gov/bulkdata/CFR/2025/title-29/CFR-2025-title29-vol5.xml
  3. Guidance Manual for Compliance with the Surface Water Treatment Rules: Turbidity Provisions, EPA 815-R-20-004 (U.S. EPA) — https://www.epa.gov/sites/default/files/2020-06/documents/swtr_turbidity_gm_final_508.pdf
  4. Disinfection Profiling and Benchmarking Technical Guidance Manual, EPA 815-R-20-003 (U.S. EPA) — https://www.epa.gov/system/files/documents/2022-02/disprof_bench_3rules_final_508.pdf
  5. Cross-Connection Control Manual, EPA 816-R-03-002 (U.S. EPA) — https://www.epa.gov/sites/default/files/2015-09/documents/epa816r03002_0.pdf
  6. Formula/Conversion Table for Water Treatment Plant and Water Distribution Systems, September 2026 (Florida Department of Environmental Protection) — https://floridadep.gov/sites/default/files/DW-DS%20Formula%20Sheet%20September%202026.pdf
  7. Formula/Conversion Table, revised February 24, 2014, the cross-check edition (Florida Department of Environmental Protection) — https://floridadep.gov/sites/default/files/dw-abcd-formula_0.pdf
  8. pH and Water, USGS Water Science School (U.S. Geological Survey) — https://www.usgs.gov/water-science-school/science/ph-and-water
  9. Turbidity and Water, USGS Water Science School (U.S. Geological Survey) — https://www.usgs.gov/water-science-school/science/turbidity-and-water
  10. Hardness of Water, USGS Water Science School (U.S. Geological Survey) — https://www.usgs.gov/water-science-school/science/hardness-water
  11. Drinking Water Operator Certification Exam Study Help (Utah Department of Environmental Quality, Division of Drinking Water) — https://deq.utah.gov/ddw/study-help
  12. Minnesota Rules 9400.1000, Examinations (Minnesota Office of the Revisor of Statutes) — https://www.revisor.mn.gov/rules/9400.1000/

The exam length (100 questions) and pass mark (70%) of the Full Mock Exam come from the Utah and Minnesota sources. Your state sets its own exam: check its own study material too.