Requirements by state

Illinois water operator certification

Reviewed 2026-07-29

Quick answer

How do I get certified as a water operator in Illinois?

Illinois certifies drinking water operators on a Class D (distribution/storage only) to Class A (advanced treatment) scale and wastewater operators on a separate Class 4 (lowest) to Class 1 (highest) scale, both through the IEPA. Drinking water certification costs $10 to request the exam plus $30 to apply; wastewater certification currently carries no fee at all. Both renew every 3 years, and Illinois accepts qualifying out-of-state certifications by reciprocity.

Last reviewed 2026-07-29

See how Illinois compares to every other jurisdiction in the national comparison matrix, or check reciprocity between states if you are moving.

Certifying agency: Illinois Environmental Protection Agency (IEPA), Operator Certification Unit

Hold a high school diploma or equivalent and pass the class-specific IEPA exam with a score of 70% or higher
Document the on-site experience hours required for the class, reducible up to 50% through approved coursework, college credit, or related field experience
Apply for reciprocal certification if already certified in another state, territory, or country with comparable standards, rather than retesting
Complete continuing education hours within the 3-year certification period to renew, two-thirds of which must be technical

Water treatment

D: Class D , Pumpage, storage, or distribution only, no treatment. 890 hours of experience required.
C: Class C , Chemical feed only (disinfection, fluoridation, stabilization). 1,780 hours of experience required.
B: Class B , Filtration and aeration systems. 5,340 hours of experience required.
A: Class A , Advanced treatment: coagulation, lime softening, UV, or membrane filtration. 5,340 hours of experience required.

Exam: IEPA-administered written exam, minimum 70% passing score, offered monthly at six locations (Champaign, Edwardsville, Elgin, Marion, Rockford, Springfield).
Education minimum: High school diploma or equivalent for every class.
Experience minimum: Class D: 890 hours. Class C: 1,780 hours. Class B: 5,340 hours. Class A: 5,340 hours.
Application / certification fee: $10 initial exam request fee, plus $30 for full certification application review; a $10 restoration fee applies to a late renewal.
Continuing education: Classes A and B: 30 hours per 3-year renewal, at least two-thirds technical. Classes C and D: 15 hours per 3-year renewal, at least two-thirds technical.
Renewal cycle: 3 years
Reciprocity: Reciprocal certification without examination is available for operators certified in another U.S. state, territory, or country, by application with proof the existing certificate is valid and current, and written authorization for Illinois to verify credentials with the issuing jurisdiction. A separate path exists for U.S. Armed Forces-trained operators, requiring 3 years of hands-on experience for Class A or B, 1 year for Class C, or 6 months for Class D.

Certificates expire 3 years from July 1 of the issue year. Class D is distribution/storage only with no treatment component, functionally similar to a distribution-only class in other states even though Illinois does not split water treatment and distribution into two separate discipline names.

Water distribution

D: Class D , Distribution and storage systems with no treatment beyond pumpage. 890 hours of experience required.

Exam: Same IEPA-administered written exam program as water treatment; Class D is the distribution-only certificate on the same A-D scale.
Experience minimum: 890 hours of relevant on-site experience for Class D.
Application / certification fee: $10 exam request fee plus $30 certification application review, same as treatment.
Continuing education: 15 hours per 3-year renewal, at least two-thirds technical.
Renewal cycle: 3 years
Reciprocity: Same reciprocal certification pathway as water treatment, including the military-experience path requiring 6 months of hands-on experience for Class D.

Illinois does not name water distribution as a separate discipline from water treatment: Class D on the shared A-D scale is the distribution-only certificate, so this entry mirrors water treatment's Class D exactly rather than describing an independent license type.

Wastewater treatment

4: Class 4 , Entry-level municipal wastewater class. 1 year of hands-on operational experience required.
3: Class 3 , 2 years of hands-on operational experience required.
2: Class 2 , 4 years of hands-on operational experience required.
1: Class 1 , Highest municipal wastewater class. 6 years of hands-on operational experience required.
K: Class K , Industrial, facility-specific certification, tied to one facility. Cannot be issued through reciprocity.
R: Class R , General industrial water remediation certificate.

Exam: IEPA Operator Certification Unit administers exams monthly at three sites statewide, scheduled first-come, first-served.
Education minimum: High school diploma or equivalent for the municipal Class 1 to 4 scale.
Experience minimum: Class 4: 1 year. Class 3: 2 years. Class 2: 4 years. Class 1: 6 years. Up to 50% of the requirement can be substituted through approved wastewater coursework, college credit, or related field experience.
Application / certification fee: No fees are currently charged for wastewater operator certification in Illinois.
Continuing education: Classes 1 and 2: 30 hours per 3-year period, at least 20 hours technical wastewater treatment. Classes 3 and 4: 15 hours per 3-year period, at least 10 hours technical.
Renewal cycle: 3 years
Reciprocity: Illinois recognizes qualifying out-of-state wastewater certifications based on individual qualifications, though the facility-specific Class K certification cannot be issued through reciprocity.

Class 1 is the highest municipal wastewater classification and Class 4 the lowest, the reverse letter-to-number direction of the drinking water A-D scale, a real point of confusion between the two Illinois programs. Certificates expire 3 years from July 1 of the issue year, matching drinking water's cycle even though the two programs are otherwise administered as separate tracks within IEPA.

Wastewater collection

CSO: Collection System Operator , A voluntary Illinois wastewater collection system operator certification, separate from the mandatory Class 1 to 4 treatment scale.

Exam: Voluntary certification track offered alongside the mandatory Class 1 to 4 wastewater treatment operator program.
Application / certification fee: No fees are currently charged for wastewater operator certification in Illinois, including the collection system track.

Illinois' Collection System Operator credential is voluntary rather than a state mandate to operate a collection system, similar in spirit to how some other states treat wastewater collection as an employer-required rather than state-required certificate. This site could not confirm a published hours/experience table specific to this voluntary track distinct from the municipal treatment classes, so that figure is omitted here rather than guessed.

Illinois runs drinking water and wastewater certification as two separate programs inside the same agency, the IEPA, and the two programs use scales that run in opposite directions: drinking water goes from Class D (lowest) up to Class A (highest), while wastewater goes from Class 4 (lowest) up to Class 1 (highest). Knowing which letter or number means what for which discipline is the first thing to get straight.

Drinking water: Class D to Class A, by treatment complexity

Illinois classifies drinking water systems by what treatment they actually run, not just system size. Class D covers pumpage, storage, and distribution with no treatment (890 hours of experience). Class C covers chemical feed only, disinfection, fluoridation, or stabilization (1,780 hours). Class B covers filtration and aeration (5,340 hours). Class A covers advanced treatment: coagulation, lime softening, UV, or membrane filtration (5,340 hours, same as B but the more complex processes). Every class needs a high school diploma or equivalent and a 70% passing score on the IEPA’s own written exam, offered monthly at six sites around the state.

Applying costs $10 for the initial exam request plus $30 for the full certification application review, a $40 total. Certificates run 3 years, expiring on a fixed date, July 1 three years from issuance, with continuing education of 30 hours (Classes A/B) or 15 hours (Classes C/D) per cycle, at least two-thirds of it technical.

Wastewater: Class 4 to Class 1, the reverse direction

Wastewater runs the opposite way: Class 4 is the entry level (1 year of experience) and Class 1 is the highest (6 years), with Class 3 (2 years) and Class 2 (4 years) between them. Illinois also issues a facility-specific industrial Class K certification, a general industrial water remediation Class R, and a voluntary Collection System Operator credential separate from the mandatory treatment ladder. Unlike drinking water, wastewater operator certification currently carries no fee at all in Illinois, a real structural difference between the two programs. The same 3-year renewal cycle applies, with continuing education of 30 hours (Classes 1/2, at least 20 technical) or 15 hours (Classes 3/4, at least 10 technical).

Moving to or from Illinois

Illinois accepts reciprocal certification from another U.S. state, territory, or country without a retest, if the applicant documents a valid, current certificate and authorizes Illinois to verify it with the issuing jurisdiction. A separate path exists for operators trained in the U.S. Armed Forces, requiring hands-on experience scaled to the class (3 years for Class A or B down to 6 months for Class D) in place of a civilian work history. Illinois’s own rule specifically excludes the facility-specific industrial Class K certification from reciprocity. On the wastewater side, Illinois recognizes qualifying out-of-state certifications case by case. See reciprocity between states for the general pattern.

Where to go from here

Because Illinois grades drinking water by treatment process rather than population size, knowing exactly what your plant does, chemical feed only versus full filtration, determines which class applies. Use the operator-math trainer for the pounds formula, CT disinfection, and activated-sludge math both Illinois programs test, and the process calculator for the same formulas on shift.

Sources: Illinois Environmental Protection Agency, Drinking Water Operator Certification FAQs (epa.illinois.gov/topics/drinking-water/operator-certification/faqs.html, retrieved 2026-07-29); Illinois EPA, Wastewater Operator Certification FAQs (epa.illinois.gov/topics/water-quality/wastewater-operator-certification/faqs.html, retrieved 2026-07-29); Illinois Administrative Code, Title 35, Section 681.600, Application for Reciprocal Certification, amended 11/13/2017 (law.cornell.edu). Authored by the Water Cert Prep editorial team. Not legal advice. Reviewed 2026-07-29.