Ohio · Water Treatment · Class IV
Ohio Grade 4 Water Treatment Operator Exam
The Ohio Grade 4 water treatment certification is designated Class IV and issued by Ohio Environmental Protection Agency (Ohio EPA). Highest certification for chief operators and superintendents at the largest, most complex systems.
Applied math is a significant part of the Ohio Class IV exam.
Practicing calculations like dosage, detention time, and loading before test day is one of the most effective ways to prepare, alongside reviewing your state’s official exam content outline.
Exam facts
| Grade level | Class IV |
|---|---|
| Questions | 120 |
| Time limit | 210 minutes |
| Passing score | 70% |
| Difficulty | Expert |
| Exam administered by | Association of Boards of Certification (ABC), administered for Ohio EPA |
Prerequisites for Class IV
- Grade 3 certification
- 4+ years of operating experience including supervisory time
- College coursework or degree (varies by state)
Confirm exact requirements with Ohio Environmental Protection Agency (Ohio EPA).
What's on the exam
- Coagulation and flocculation
- Sedimentation and clarification
- Filtration (conventional, direct, membrane)
- Disinfection and disinfection byproducts
- Corrosion control and stabilization
- Source water and watershed protection
- Plant-wide optimization
- Management, budgeting, and staffing
The math on the Water Treatment exam
These calculations are commonly included in water treatment operator exam preparation and may appear on your exam depending on your certification level and state. Practicing them is one of the most effective ways to prepare.
- Chemical dosage (mg/L to lbs/day)
- Chlorine demand and CT calculations
- Detention time
- Filter loading and backwash rate
- Flow rate and velocity
- Percent strength of solutions
Free Class IV practice questions
Sample questions with full explanations at this level.
Take the practice quiz →Frequently asked questions
- What is the Ohio Grade 4 water treatment certification called?
- In Ohio, the Grade 4 water treatment certification is designated Class IV, issued by Ohio Environmental Protection Agency (Ohio EPA).
- How many questions are on the exam and what score do I need?
- The exam has about 120 questions with a 210-minute time limit, and you need 70% to pass. It is administered by Association of Boards of Certification (ABC), administered for Ohio EPA.
- What are the prerequisites for Class IV in Ohio?
- Typical prerequisites: Grade 3 certification; 4+ years of operating experience including supervisory time; College coursework or degree (varies by state). Exact requirements are set by Ohio Environmental Protection Agency (Ohio EPA).