Pass your water or wastewater operator certification exam.

WPI-aligned practice tests for every water-industry operator certification, covering drinking water, wastewater, distribution, and collections. Every level, every topic, with a plain-English explanation on every question.

What are you studying for?

Water treatment Wastewater treatment Water distribution Wastewater collection

Studying for a specific state? (optional)

Browse the practice tests

Listed as a study resource by the Montana DEQ, Tennessee DEC and the Nevada Water Environment Association.

101 practice tests
4,300+ questions
$0 to practice
I have been studying on your site since July and recently passed my Class 1 test with an 84. I credit your site for that!
Matt D.Connecticut · Passed Class 1

Which exam are you studying for?

We cover every water-industry operator certification. Choose your discipline to see the practice tests, levels, and study guides for it.

Albert on site in a hard hat and hi-vis vest, a storage tank behind him

Who writes these questions

I'm Albert, a water plant manager who has been licensed in Texas, Florida, Virginia and Delaware. I have sat for these exams myself.

Most plants keep a binder of study questions for their operators. I thought it would work better on a computer, where you find out what you missed and why, right away. So I built one. Operators flag the questions they think are wrong and I rewrite those, which is the reason the bank keeps getting better.

More about the site →

Operator math course

The math is what fails most operators

Operator math is the lowest scoring category on this site. This course turns it into your easiest points: every formula on the exam, set up and worked by hand step by step, built from the same questions you practice on here.

You get 11 video modules, 74 quiz questions that tell you which mistake you made, and a formula sheet to keep beside you while you study. $49 one time, and pass or your money back for 6 months.

Continue to the Course

The practice tests stay free. They always will.

Pass or your money back, good for a full 6 months
The course
Water Operator Math
11
modules, worked by hand on video
3.5
hours of instruction, and then some
74
quiz questions, explained
3
page formula sheet to print
∞
lifetime access, plus email help when you get stuck
$49 one time · Module 3 free

Why study with us

Three reasons operators come back.

Practice tests free, forever

Every practice question and explanation on this site is 100% free, and that's not changing.

Explanations that teach

Every question comes with a plain-English explanation, so you actually learn the material, not just memorize it.

Study anywhere

Works on your phone in the truck, on a desktop at the plant, or on the couch. No app to install.

Frequently asked questions

Is this really free?
Yes. Every practice test on this site is 100% free, and always will be. To keep it that way, the site may feature sponsors or offer optional paid resources like study courses, but the practice tests themselves stay free.
Are these the exact questions on the real exam?
No. These are independent practice tests designed to mirror the style, depth, and topic distribution of water operator certification exams. The actual content and format of state exams vary. Always check with your state's certification program for the official scope.
What's the difference between Level 1, 2, 3, and 4?
These mirror the four operator classifications used by the Water Professionals International (WPI) and most state programs. Level 1 covers entry-level small systems, Level 2 is intermediate, Level 3 is advanced, and Level 4 is for operators of large, complex water systems. Most states accept WPI-aligned exams.
Do I need to create an account?
No. You can take every test as a guest. Creating a free account is optional, it lets us save your scores across devices and show you which topics you've mastered over time.
Is my state's exam covered?
If your state uses WPI-aligned operator classifications (which most do), the four levels here will match. If your state uses a different framework, the topic-specific tests still cover the underlying material on virtually every drinking-water operator exam.
How often are new questions added?
We expand the question bank regularly. If you spot an error, or have a suggestion for a topic we should cover, please reach out from the About page.