How to Become a Water Operator in Illinois (Illinois EPA)

Illinois certifies drinking-water operators through the Illinois EPA Drinking Water Operator Certification Program. The path has a useful feature: you can pass the exam first and become an Operator-in-Training (OIT) while you build the required experience. Here's the full route, plus one naming gotcha to avoid.

Requirements and fees change. Confirm current details on the Illinois EPA Operator Certification site before applying.

Key takeaways

• Illinois drinking-water classes are A, B, C, D — and here Class A is the highest (most complex treatment), down to Class D (pumpage/storage/distribution).
• Pass the exam (70%) with a high-school diploma/GED; you become an Operator-in-Training (OIT) valid for six years while you log experience.
• Experience by class: D ≈ 890 hours, C ≈ 1,780, B and A ≈ 5,340 hours. Apply with references and a verification letter.
• Practice with the drinking-water level tests and your Illinois state page.

Heads up: which way the numbers go

Illinois uses letters (A–D) for drinking water, with Class A the highest. Don't confuse this with Illinois wastewater, which uses Class 1–4 where Class 1 is the highest (inverted from most states). This guide is the drinking-water path; the wastewater path is separate.

Step 1 — Know the class you need

Illinois drinking-water classes are defined by the treatment a facility uses:

• Class A — complex treatment systems (highest).
• Class B — facilities with aeration, filtration, or ion exchange.
• Class C — facilities with chemical feed only.
• Class D — facilities limited to pumpage, storage, or distribution (entry).

Step 2 — Request and take the exam

Submit a "Drinking Water Operator Certification Examination Request" with a $10 fee. If approved, Illinois EPA sends a Letter of Admission and exam schedule. You need a high-school diploma/GED and a 70% passing score.

Prepare by practicing questions and reviewing the explanation on each. Use our practice tests — start with a 25-question quick quiz, then the 50-question practice exam and full-length simulation.

Step 3 — Become an Operator-in-Training, then log experience

Once you pass, you're an Operator-in-Training (OIT) — a certificate valid for six years. Use that window to accumulate the required hands-on experience:

• Class D — about 890 hours.
• Class C — about 1,780 hours.
• Class B / Class A — about 5,340 hours.

Step 4 — Apply for full certification

When you've met the experience, submit the application for certification with the $30 review fee, including:

• three references who can verify your character and experience,
• a letter of verification from a water-supply official, and
• transcripts/course certificates if you're claiming educational credit.

Step 5 — Renew every three years

Certificates run three years. Class A and B operators need 30 renewal training hours; Class C and D need 15 hours — with at least two-thirds on technical water-treatment/distribution topics.

A note on wastewater

Illinois wastewater operators are certified separately, using Class 1–4 (Class 1 highest), and collection-system certification is voluntary. See the collections hub and your Illinois state page.

Next steps

1. Confirm your class and current rules on the Illinois EPA Operator Certification site.
2. Read certification levels explained for how Illinois fits the national ladder.
3. Start practicing from your Illinois state page — and create a free account to save your scores and track weak topics.