Operator Certification Exams

Additional Resources

• Useful Water Wastewater Formulas

More robust math formula sheets will be available to test takers once the new exams go live in January 2027, and will offer more variety to solving math problems.

• Math Formulas for Drinking Water Treatment and Distribution Exams
• Math Formulas for Wastewater Treatment Exams 

Testing Center

• PSI Test Center Experience - video
• Testing Locations - On the PSI webpage, please follow the instructions below to check the current available dates.
  • Select “Check for Available Dates”
  • Choose the “Onsite (Test Center)” option for any exam
  • Select “Continue” under the Fee Policy statement
  • Select the “Onsite (Test Center)” option and follow the prompts to pull up a list of locations and a map
• Test center examinees will be provided scratch paper and pencil and may bring their own non-programmable calculator. The math formula sheet will be available electronically under the resource tab during the exam.

Remote Online Proctoring

It is critical that examinees read the Candidate Handbook and prepare for a successful remote exam session.

• PSI Online Proctoring Experience - video
• Online Proctoring Compatibility Check - Verify support for your computer's operating system, computer hardware and required internet bandwidth.
• If possible, use your personal computer rather than a work computer. During the check-in process, you will be required to download a secure browser for use while you take the exam. Work computers often have security systems in place that prevent the secure exam browser from downloading and launching. If you need assistance to download applications or software to your computer, you should not take a remote exam with that computer.
• Remote examinees are allowed two sheets of blank scratch paper and a pencil or white board and dry erase marker, and a non-programmable calculator to work math problems. The math formula sheet will be available electronically under the resource tab during the exam.

In January of 2027, the department will be transitioning to standardized operator certification exams*, which will be available through the state’s existing contract with Water Professionals International (WPI) for computer-based testing. These exams are built by operators for operators and go through a rigorous psychometric process to ensure they are fair and valid. 

*Standardized exams are not available for Concentrated Animal Feeding Operation (CAFO) exams, so no changes are anticipated for CAFO exams. 

The new exams will go live Jan. 1, 2027. The department does not anticipate a break in exam services, with the existing exams being available up until the switch to standardized exams. The chart below provides the crosswalk for each exam and corresponding "need to know" (NTK) criteria that is applicable to Missouri exams. Each exam type and level has a separate detailed NTK document, provided by WPI, that includes study references. WPI refers to different levels of exams as operator class 1 (lowest) through 4 (highest). 

Test takers can access practice exam questions on WPI's Sample Exam Questions webpage. More robust math formula sheets will be available to test takers once the new exams go live in January 2027, and will offer more variety to solving math problems.

• Math Formulas for Drinking Water Treatment and Distribution Exams
• Math Formulas for Wastewater Treatment Exams 

All exams will be 100 questions, with an additional 10 sample questions scattered throughout the exam that will not be scored. Sample questions allow performance statistics to be gathered on individual questions before placing them into exams for score, which improves the validity of future exams. Visit WPI’s Standardized Exams webpage to learn more about the steps WPI uses to create NTKs and standardized exams and how you can be involved in exam content development.