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The water distribution study center

Every module and guide for the water distribution exam, organized by the exam's own duty list and weights. Free, no signup.

Closed book. About 100 questions. Formula sheet provided. Scaled score of 70 to pass.

Class I is the entry-level license, whatever your state calls the grade. Weights below are the 2025 WPI/ABC Need-to-Know Criteria, Class I.

Start here

1Take a practice test cold. It shows you your weak duties before you spend a week rereading.
2Study the map below: heaviest duty first, your weakest topics first.
3Drill the math until the steps are boring, then practice again, timed.

A comfortable runway is six weeks: a duty or two a week, math in week five, timed tests in week six.

Take the practice test

What's on the exam, and what covers it

Four duties, weighted by the exam itself. The minutes are real read times; a first pass through everything below is about an hour and a half, and passing takes running it more than once. Weights from the 2025 WPI/ABC Need-to-Know Criteria, Class I.

35%

System components

 

From the tank to the tap.

30%

Equipment installation, operation, maintenance and repair

 
20%

Security, safety, admin and public relations

 
15%

Water quality monitoring and lab

 
~9%

of every duty above is calculations

The Class I split runs about 45/55 recall to application: know the parts, then practice applying them.

Drill the math

About 9% of the questions are calculations, and they are the ones people leave blank. Most are five formula families: dosage, detention time, flow, the 8.34 conversion, and area and volume. Learn the steps, then make the calculator show its work until you do not need it.

Water distribution math

The distribution calculations worked in steps: pressure, head, flow and dosage.

Operator math fundamentals

The base layer: units, conversions, and the 8.34 relationship everything else stands on.

Check your readiness

Test yourself before the state does

The practice bank is the fastest way to find your weak duties. Use it cold on day one, then timed in your last week.

Start here

Practice tests

Includes the water distribution bank: original questions, every answer backed by a source, weak topics highlighted. Practice or timed.

Take a practice test
8.34

Operator calculator

8.34 lb/gal is the number the exam never stops using. The calculator runs dosage, detention time and loading with worked steps, not just an answer.

Open the operator calculator
Print it

Formula sheets

Your water distribution formulas on one page, grouped the way the exam groups them, next to the other three disciplines.

Open the formula sheets

Then check your state's rules

The exam is a national standard; the license comes from your state. Find your state on the operator door's map for grades, applications and renewal. Then compare across states: what certification costs, whether your license transfers, and the CEUs renewal takes.

The other exam tracks

Water treatment · Wastewater treatment · Wastewater collection

Each is built the same way from its own exam's weights. Or head back to the operator door to pick your track and find your state. A free resource from Ziptility. We make software for small water systems.