ABC/WPI Water and Wastewater Operator Practice Test
Class I and II practice in four disciplines, weighted like WPI’s 2025 Need-to-Know Criteria.
What is the maximum holding time for drinking water coliform samples under federal method rules?
630 original questions with explanations · 8 practice exams · a free drill for every exam
Choose your exam
Water Professionals International (formerly the Association of Boards of Certification, ABC) writes standardized operator exams used by many state certification programs. Each Class I and II exam has 100 scored questions plus up to 10 unscored pretest items.
Water treatment
- Water Treatment Class I Practice Test (ABC/WPI)
100-question practice exam
- Water Treatment Class II Practice Test (ABC/WPI)
100-question practice exam
Water distribution
- Water Distribution Class I Practice Test (ABC/WPI)
100-question practice exam
- Water Distribution Class II Practice Test (ABC/WPI)
100-question practice exam
Wastewater treatment
- Wastewater Treatment Class I Practice Test (ABC/WPI)
100-question practice exam
- Wastewater Treatment Class II Practice Test (ABC/WPI)
100-question practice exam
Wastewater collection
- Wastewater Collection Class I Practice Test (ABC/WPI)
100-question practice exam
- Wastewater Collection Class II Practice Test (ABC/WPI)
100-question practice exam
Not built yet: Class III and IV, very small water system, lab analyst and industrial waste exams. States set time limits and passing scores, so our practice exams show your score by content area.
Sit a full practice exam
100 questions in the official content counts, with a score for every area and an explanation for every option.
Or pick your exam belowCommon questions
Is ABC the same as WPI?
Yes. The Association of Boards of Certification is now Water Professionals International; ABC Testing is its testing service.
Does my state use the WPI exam?
Many state programs do, but not all, and some use older editions or custom exams built from WPI items. Ask your state certifying authority which exam and edition you will take.
What is the passing score on WPI exams?
Each state program sets its own passing score, time limit and fees; WPI reports results through the state, not to candidates.
What changed in 2025?
WPI released new 2025 standardized exams with updated Need-to-Know Criteria, content-area counts and calculation shares, and Spanish versions of Classes I and II.
Practice by topic
- Source Water and Wells
- Coagulation, Sedimentation and Filtration
- Water Disinfection and Chlorination
- Corrosion, Iron, Manganese and Fluoride
- Water Lab and Sampling
- Water Mains, Valves and Hydrants
- Distribution Hydraulics and Storage
- Cross-Connection and Backflow
- Drinking Water Regulations
- Water Math
- Pumps, Motors and Equipment
- Operator Safety
- Management, Records and Customer Service
- Preliminary and Primary Treatment
- Activated Sludge
- Trickling Filters, RBCs and Ponds
- Sludge Digestion and Biosolids
- Wastewater Disinfection and Effluent
- Wastewater Lab and Sampling
- Wastewater Permits and Regulations
- Wastewater Math
- Sewer Cleaning and Inspection
- Collection System Maintenance
- Inflow, Infiltration and Overflows
- Lift Stations
Exam rules and counts checked November 2026 on gowpi.org: WPI: 2025 Need-to-Know Criteria · WPI: Information for examinees.
Game Assessment Prep is an independent practice site, not affiliated with or endorsed by Water Professionals International (WPI, formerly ABC), the California State Water Resources Control Board or the Texas Commission on Environmental Quality. Every question is original; none is taken from a certification exam, an official study guide or another prep provider.