ILLINOIS PLUMBING INSPECTOR EXAM QUESTIONS AND CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A | INSTANT DOWNLOAD PDF
Core Domains
*- Illinois Plumbing Code (77 Ill. Adm. Code 890) Requirements*
*- Pipe Sizing and Drainage Fixture Units*
*- Venting Systems and Trap Arm Requirements*
*- Backflow Prevention and Cross-Connection Control*
*- Water Heater Safety and Temperature-Pressure Relief Valves*
*- Cleanout Spacing and Drainage System Maintenance*
*- Plumbing Fixture Installation Standards*
*- Professional Ethics and Inspector Responsibilities*
*- Regulatory Compliance and Legal Requirements*
*- Real-World Inspection Scenarios and Decision-Making*
The Illinois Plumbing Inspector Exam assesses the knowledge and skills required for certified plumbing
inspectors to enforce the Illinois Plumbing Code effectively. This multiple-choice examination includes
scenario-based questions that test foundational theory, applied professional knowledge, regulatory
compliance, ethics, and real-world decision-making. Candidates must demonstrate competency in pipe sizing,
venting requirements, backflow prevention, fixture installation, and safety devices. The exam emphasizes
practical application of code provisions to actual inspection situations, ensuring inspectors can identify
violations and make informed compliance decisions in diverse plumbing systems across residential,
commercial, and industrial settings.
SECTION ONE: QUESTIONS 1–100
,Question 1
What is the maximum spacing required for cleanouts in horizontal drainage lines 4 inches or less in size
according to the Illinois Plumbing Code?
A. 100 feet
B. 150 feet
C. 50 feet
D. 75 feet
🟢 C. 50 feet
🔴 RATIONALE: Section 890.420 of the Illinois Plumbing Code explicitly states that cleanouts shall be not
more than 50 feet apart, including the developed length of the cleanout pipe, in horizontal drainage lines of 4
inches or less size.
Question 2
Which backflow prevention device is the minimum base requirement for all State of Illinois plumbing
installations?
A. Atmospheric vacuum breaker
B. Double check backflow preventor
C. Pressure vacuum breaker
D. Reduced pressure zone assembly
🟢 B. Double check backflow preventor
,🔴 RATIONALE: The Illinois Plumbing Code requires a double check backflow preventor as the minimum base
requirement for all State of Illinois installations, as stated in the official backflow prevention guidelines.
Question 3
What is the minimum diameter requirement for an individual vent pipe according to Illinois Plumbing Code
Section 890.1580?
A. 1 inch or half the drain diameter
B. 1¼ inches or half the drain diameter
C. 1½ inches or one-third the drain diameter
D. 2 inches or equal to the drain diameter
🟢 B. 1¼ inches or half the drain diameter
🔴 RATIONALE: Section 890.1580 specifies that the diameter of an individual vent shall be at least 1¼ inches
or at least half the diameter of the drain to which it connects, whichever is greater.
Question 4
At what maximum distance must cleanouts be placed in horizontal drainage lines exceeding 10 inches in size?
A. 50 feet
B. 100 feet
C. 125 feet
D. 150 feet
🟢 D. 150 feet
, 🔴 RATIONALE: Section 890.420 states that cleanouts shall not be more than 150 feet apart, including the
developed length of the cleanout pipe, in horizontal drainage lines exceeding 10 inches in size.
Question 5
What safety device must be installed on all equipment used for heating or storing hot water at the time of
installation?
A. Flow control valve
B. Temperature and pressure relief valve
C. Check valve
D. Pressure reducing valve
🟢 B. Temperature and pressure relief valve
🔴 RATIONALE: Section 890.1230 requires that all equipment used for heating water or storing hot water shall
be provided, at the time of installation, with the required relief valve (temperature and pressure relief valve).
Question 6
An inspector encounters a water softener installation. Within what distance must a properly sized and vented
drain be located from the water softener?
A. 3 feet
B. 5 feet
C. 7 feet
D. 10 feet
ANSWERS) PLUS RATIONALES 2026 Q&A | INSTANT DOWNLOAD PDF
Core Domains
*- Illinois Plumbing Code (77 Ill. Adm. Code 890) Requirements*
*- Pipe Sizing and Drainage Fixture Units*
*- Venting Systems and Trap Arm Requirements*
*- Backflow Prevention and Cross-Connection Control*
*- Water Heater Safety and Temperature-Pressure Relief Valves*
*- Cleanout Spacing and Drainage System Maintenance*
*- Plumbing Fixture Installation Standards*
*- Professional Ethics and Inspector Responsibilities*
*- Regulatory Compliance and Legal Requirements*
*- Real-World Inspection Scenarios and Decision-Making*
The Illinois Plumbing Inspector Exam assesses the knowledge and skills required for certified plumbing
inspectors to enforce the Illinois Plumbing Code effectively. This multiple-choice examination includes
scenario-based questions that test foundational theory, applied professional knowledge, regulatory
compliance, ethics, and real-world decision-making. Candidates must demonstrate competency in pipe sizing,
venting requirements, backflow prevention, fixture installation, and safety devices. The exam emphasizes
practical application of code provisions to actual inspection situations, ensuring inspectors can identify
violations and make informed compliance decisions in diverse plumbing systems across residential,
commercial, and industrial settings.
SECTION ONE: QUESTIONS 1–100
,Question 1
What is the maximum spacing required for cleanouts in horizontal drainage lines 4 inches or less in size
according to the Illinois Plumbing Code?
A. 100 feet
B. 150 feet
C. 50 feet
D. 75 feet
🟢 C. 50 feet
🔴 RATIONALE: Section 890.420 of the Illinois Plumbing Code explicitly states that cleanouts shall be not
more than 50 feet apart, including the developed length of the cleanout pipe, in horizontal drainage lines of 4
inches or less size.
Question 2
Which backflow prevention device is the minimum base requirement for all State of Illinois plumbing
installations?
A. Atmospheric vacuum breaker
B. Double check backflow preventor
C. Pressure vacuum breaker
D. Reduced pressure zone assembly
🟢 B. Double check backflow preventor
,🔴 RATIONALE: The Illinois Plumbing Code requires a double check backflow preventor as the minimum base
requirement for all State of Illinois installations, as stated in the official backflow prevention guidelines.
Question 3
What is the minimum diameter requirement for an individual vent pipe according to Illinois Plumbing Code
Section 890.1580?
A. 1 inch or half the drain diameter
B. 1¼ inches or half the drain diameter
C. 1½ inches or one-third the drain diameter
D. 2 inches or equal to the drain diameter
🟢 B. 1¼ inches or half the drain diameter
🔴 RATIONALE: Section 890.1580 specifies that the diameter of an individual vent shall be at least 1¼ inches
or at least half the diameter of the drain to which it connects, whichever is greater.
Question 4
At what maximum distance must cleanouts be placed in horizontal drainage lines exceeding 10 inches in size?
A. 50 feet
B. 100 feet
C. 125 feet
D. 150 feet
🟢 D. 150 feet
, 🔴 RATIONALE: Section 890.420 states that cleanouts shall not be more than 150 feet apart, including the
developed length of the cleanout pipe, in horizontal drainage lines exceeding 10 inches in size.
Question 5
What safety device must be installed on all equipment used for heating or storing hot water at the time of
installation?
A. Flow control valve
B. Temperature and pressure relief valve
C. Check valve
D. Pressure reducing valve
🟢 B. Temperature and pressure relief valve
🔴 RATIONALE: Section 890.1230 requires that all equipment used for heating water or storing hot water shall
be provided, at the time of installation, with the required relief valve (temperature and pressure relief valve).
Question 6
An inspector encounters a water softener installation. Within what distance must a properly sized and vented
drain be located from the water softener?
A. 3 feet
B. 5 feet
C. 7 feet
D. 10 feet
