Trade certification · Water operator
Water & Wastewater Operator (WPI/ABC Class I) — Practice Exam
Entry-level (Class I) operator certification in four tracks: drinking water treatment, water distribution, wastewater treatment and wastewater collection. Covers processes, equipment, lab tests, regulations, safety and operator math. Pick your track before you start.
Questions last checked against the official sources on October 6, 2026.
The real exam at a glance
- Exam
- 100 scored questions per exam (up to 10 more unscored)
- Math
- About 10% calculation questions; a formula sheet is provided
- Water treatment
- Process 31, equipment 26, lab 16, source water 15, safety/admin 12
- Wastewater treatment
- Equipment 39, process 38, safety/admin 13, lab 10
- Water distribution
- Components 35, equipment 30, safety/admin 20, water quality 15
- Wastewater collection
- Equipment 27, collection O&M 27, lift stations 18, monitoring 14, safety/admin 14
What you'll practise
Try a question
Under the Ten States Standards, what conditions must trigger a pumping station alarm?
- Power failure, high wet well level, pump failure, unauthorized entry or other malfunction
- Only fire inside the station building
- Only a fire inside the station building, since other problems can wait for the next scheduled visit
- Only scheduled maintenance
Show the answer
A. Power failure, high wet well level, pump failure, unauthorized entry or other malfunction — Ten States Standards 46.
Sample questions by topic (in English)
- WT treatment: coagulation
- WT treatment: filtration
- WT treatment: disinfection
- WT treatment: operation
- WT math
- WT lab
- WT equipment
- WT source water
- WT safety
- WT admin
- WW secondary: activated sludge
- WW secondary: fixed film
- WW solids
- WW effluent
- WW equipment: aeration
- WW equipment: pumps
- WW equipment: instruments
- WW lab
- WW safety
- WW process
- WD components: mains
- WD components: valves
- WD components: hydrants
- WD components: storage
- WD components: meters
- WD equipment: installation
- WD equipment: repair
- WD equipment: maintenance
- WD quality
- WD admin
- WC system
- WC O&M
- WC lift stations
- WC monitoring
- WC safety
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Questions about the Water/Wastewater Operator
Is this the official Water/Wastewater Operator?
No. Semplr is independent and not affiliated with the exam body. We write every question ourselves, in the official format and at the official level.
What is the real Water/Wastewater Operator like?
Exam: 100 scored questions per exam (up to 10 more unscored). Math: About 10% calculation questions; a formula sheet is provided. Water treatment: Process 31, equipment 26, lab 16, source water 15, safety/admin 12. Wastewater treatment: Equipment 39, process 38, safety/admin 13, lab 10. Water distribution: Components 35, equipment 30, safety/admin 20, water quality 15. Wastewater collection: Equipment 27, collection O&M 27, lift stations 18, monitoring 14, safety/admin 14.
How is my practice marked?
Instantly. You see your score against the pass mark, and an explanation for every question — including the ones you got right.
Can I take it on my phone?
Yes. The whole mock exam works on a phone, and your progress is saved in your browser.
Ready for a full run?
One sitting, real timing, then your score against the pass mark.
Start the free mock exam