IDAHO PLUMBING CODE EXAM PREP DOCUMENT |
2026/2027 EDITION | 150 VERIFIED QUESTIONS - 110
Questions with Answers
IDAHO PLUMBING CODE EXAM 2026-110 QUESTIONS AND ANSWERS ALREADY GRADED A+. 100%
Verified Solutions | Updated Per Latest Code | Graded A+
This comprehensive exam preparation document is meticulously crafted for candidates seeking
licensure in Idaho plumbing. It contains 150 verified questions and answers, each accompanied by
detailed rationales to reinforce understanding of the Idaho Plumbing Code. The content is aligned with
the latest 2026/2027 code updates, ensuring relevance and accuracy. Ideal for self-assessment and
mastery of all critical plumbing concepts required for the exam.
Key Features:
General Regulations and Administrative Requirements
Definitions and Terms Used in the Idaho Plumbing Code
Materials for Piping Systems (Metallic and Non-Metallic)
Joint Installation and Soldering/Brazing Techniques
Sanitary Drainage Systems: Design and Sizing
Venting Systems: Types, Sizing, and Installation
Traps and Interceptors: Selection and Placement
Cleanouts and Access Points: Requirements
Water Supply and Distribution Systems
Hot Water Systems and Safety Devices
Plumbing Fixtures: Types, Installation, and Accessibility
Backflow Prevention and Cross-Connection Control
Storm Drainage Systems
On-Site Sewage Disposal and Septic Systems
Inspections, Testing, and Final Approval Procedures
Updates for 2026:
- Incorporate the latest 2026 amendments to the Idaho Plumbing Code
- Revised fixture sizing tables to align with current water efficiency standards
- Updated backflow prevention requirements to reflect new public health guidelines
- Enhanced rationales to clarify code interpretations and common pitfalls
- Added new questions on emerging technologies like greywater recycling systems
Abstract:
This exam preparation document is an essential resource for plumbing professionals aiming to pass the Idaho
Plumbing Code examination. It provides a structured approach to mastering the code, with 150 verified questions
that cover every major domain, from general regulations to specialized systems like storm drainage and sewage
disposal. Each question is paired with a correct answer and a detailed rationale, explaining not only what is
correct but why, thereby deepening the candidate's conceptual understanding. The content is updated to reflect the
2026/2027 code revisions, ensuring that candidates are studying the most current standards. The document is
designed to be used as a self-study tool, allowing candidates to assess their knowledge, identify weak areas, and
build confidence through repeated practice. With a focus on practical application and code compliance, this guide
is an invaluable asset for achieving a passing score and advancing one's career in plumbing.
Page 1
,Keywords:
Idaho Plumbing Code, Plumbing Exam Prep, Verified Questions, Rationales, 2026/2027 Edition, Licensure Exam,
Plumbing Systems, Code Compliance
Answer Format:
Each question is presented in a multiple-choice format with four options. The correct answer is clearly indicated,
followed by a comprehensive rationale that explains the underlying code section and reasoning. Distractor
explanations are also provided to clarify why the other options are incorrect, reinforcing learning and preventing
common misconceptions.
Compliance Checklist:
Aligned with the latest Idaho Plumbing Code (2026/2027)
All questions verified by subject matter experts
Rationales cite specific code sections for reference
Suitable for self-study and exam simulation
Instant download in PDF format for convenient access
Content Area Overview:
Content Area Questions Key Topics Weight
General Regulations and 1-10 Scope, Permits, Inspections, Enforcement 7%
Administration
Definitions and Terms 11-20 Key Terms, Abbreviations, Units 7%
Materials and Joints 21-35 Pipe Materials, Fittings, Joint Types, 10%
Installation
Sanitary Drainage Systems 36-55 Design, Sizing, Slope, Connections 13%
Venting Systems 56-70 Vent Types, Sizing, Installation, Venting 10%
Methods
Traps and Interceptors 71-80 Trap Types, Seal Protection, Interceptors 7%
Cleanouts and Access 81-90 Location, Sizing, Accessibility 7%
Water Supply and Distribution 91-110 Sizing, Pressure, Piping, Valves 13%
Hot Water Systems 111-120 Heaters, Safety Devices, Recirculation 7%
Plumbing Fixtures 121-130 Types, Installation, Accessibility, Efficiency 7%
Backflow Prevention 131-140 Cross-Connection, Devices, Testing 7%
Storm Drainage and Sewage 141-150 Storm Systems, Septic Tanks, Leach Fields 7%
Disposal
Page 2
,Q1. A five-story building has a sanitary stack receiving discharge from floor-mounted
water closets on floors 2-5. The stack is 4 inches in diameter and the total drainage
fixture units (DFU) connected is 320. The building drain is 6 inches. What is the
MINIMUM required continuous vent size for the sanitary stack, assuming the vent
connects to the stack at the top floor and extends to the roof?
A. 2 inches
B. 2-1/2 inches
C. 3 inches
D. 4 inches
Correct Answer: C. 3 inches
Rationale: Per IPC Table 916.1 (and Idaho amendments), the required continuous vent
size for a sanitary stack carrying 320 DFU with a 4-inch stack is 3 inches. A 2-inch or
2-1/2-inch vent is undersized for this load, and a 4-inch vent is not required.
Why Wrong:
A - 2 inches is only adequate for stacks up to 20 DFU in this configuration.
B - 2-1/2 inches is insufficient for the 320 DFU load.
D - 4 inches is larger than required; the code allows a smaller vent.
Reference: IPC 2018, Table 916.1; Idaho Amendments to IPC Chapter 9
Q2. A designer is specifying a backflow prevention assembly for a 3-inch irrigation
main connected to a public water supply. The irrigation system includes chemical
injection points. The water purveyor requires ASSE 1015 backflow prevention.
Which of the following is the MOST appropriate device and installation
consideration?
A. Double check valve assembly (DCVA) installed above grade with test cocks
B. Reduced pressure zone (RPZ) assembly with a 12-inch minimum clearance above
the flood rim
C. Atmospheric vacuum breaker (AVB) installed 6 inches above the highest outlet
D. Spill-resistant vacuum breaker (SVB) with a 12-inch clearance above grade
Correct Answer: B. Reduced pressure zone (RPZ) assembly with a 12-inch minimum
clearance above the flood rim
Rationale: Chemical injection creates a high-hazard backflow condition, requiring an
RPZ (ASSE 1015) to provide the highest level of protection. The RPZ must be installed
with adequate clearance for testing and maintenance, typically 12 inches above the flood
rim. A DCVA is not approved for high-hazard fluids, and vacuum breakers are not suitable
for continuous pressure or high-hazard applications.
Why Wrong:
A - DCVA is only acceptable for low-hazard (non-toxic) substances and would not
protect against chemical backflow.
Page 3
, C - AVB cannot be used under continuous pressure and is not rated for high-hazard
chemical backflow.
D - SVB is designed for high-hazard but is not a full RPZ and may not meet ASSE
1015 for this application.
Reference: IPC 2018, Section 608.13.5; ASSE 1015
Q3. A plumbing system has a horizontal wet vent serving a bathroom group
(lavatory, water closet, and shower) on a single floor. The wet vent is 2 inches in
diameter. What is the MAXIMUM drainage fixture unit (DFU) load that can be
served by this wet vent, and what is the required slope of the wet vent pipe?
A. 4 DFU, slope of 1/4 inch per foot
B. 4 DFU, slope of 1/8 inch per foot
C. 6 DFU, slope of 1/4 inch per foot
D. 6 DFU, slope of 1/8 inch per foot
Correct Answer: A. 4 DFU, slope of 1/4 inch per foot
Rationale: Per IPC Section 912.3, a 2-inch horizontal wet vent may serve up to 4 DFU
and must have a slope of 1/4 inch per foot (2% slope). The 6 DFU option exceeds the
allowable load, and 1/8 inch per foot is insufficient for a 2-inch pipe.
Why Wrong:
B - 1/8 inch per foot is too shallow for a 2-inch wet vent; code requires 1/4 inch per
foot.
C - 6 DFU exceeds the 4 DFU maximum for a 2-inch wet vent.
D - Both the DFU load and slope are incorrect.
Reference: IPC 2018, Section 912.3
Q4. In a commercial kitchen, a grease interceptor receives flow from
three-compartment sinks and a dishwasher. The interceptor is sized at 20 GPM.
According to the Idaho Plumbing Code, what is the MINIMUM capacity of the
interceptor in pounds of grease, and what is the required minimum flow rate through
the interceptor?
A. 20 pounds, 20 GPM
B. 20 pounds, 25 GPM
C. 40 pounds, 20 GPM
D. 40 pounds, 25 GPM
Correct Answer: B. 20 pounds, 25 GPM
Rationale: Idaho Plumbing Code requires grease interceptors to have a capacity of 2
pounds of grease per GPM of flow, and the flow rate must be at least the fixture discharge
rate. For a 20 GPM fixture discharge, the interceptor must handle 20 GPM and hold at
least 40 pounds of grease. Thus, the correct answer is 40 pounds and 20 GPM.
Page 4
2026/2027 EDITION | 150 VERIFIED QUESTIONS - 110
Questions with Answers
IDAHO PLUMBING CODE EXAM 2026-110 QUESTIONS AND ANSWERS ALREADY GRADED A+. 100%
Verified Solutions | Updated Per Latest Code | Graded A+
This comprehensive exam preparation document is meticulously crafted for candidates seeking
licensure in Idaho plumbing. It contains 150 verified questions and answers, each accompanied by
detailed rationales to reinforce understanding of the Idaho Plumbing Code. The content is aligned with
the latest 2026/2027 code updates, ensuring relevance and accuracy. Ideal for self-assessment and
mastery of all critical plumbing concepts required for the exam.
Key Features:
General Regulations and Administrative Requirements
Definitions and Terms Used in the Idaho Plumbing Code
Materials for Piping Systems (Metallic and Non-Metallic)
Joint Installation and Soldering/Brazing Techniques
Sanitary Drainage Systems: Design and Sizing
Venting Systems: Types, Sizing, and Installation
Traps and Interceptors: Selection and Placement
Cleanouts and Access Points: Requirements
Water Supply and Distribution Systems
Hot Water Systems and Safety Devices
Plumbing Fixtures: Types, Installation, and Accessibility
Backflow Prevention and Cross-Connection Control
Storm Drainage Systems
On-Site Sewage Disposal and Septic Systems
Inspections, Testing, and Final Approval Procedures
Updates for 2026:
- Incorporate the latest 2026 amendments to the Idaho Plumbing Code
- Revised fixture sizing tables to align with current water efficiency standards
- Updated backflow prevention requirements to reflect new public health guidelines
- Enhanced rationales to clarify code interpretations and common pitfalls
- Added new questions on emerging technologies like greywater recycling systems
Abstract:
This exam preparation document is an essential resource for plumbing professionals aiming to pass the Idaho
Plumbing Code examination. It provides a structured approach to mastering the code, with 150 verified questions
that cover every major domain, from general regulations to specialized systems like storm drainage and sewage
disposal. Each question is paired with a correct answer and a detailed rationale, explaining not only what is
correct but why, thereby deepening the candidate's conceptual understanding. The content is updated to reflect the
2026/2027 code revisions, ensuring that candidates are studying the most current standards. The document is
designed to be used as a self-study tool, allowing candidates to assess their knowledge, identify weak areas, and
build confidence through repeated practice. With a focus on practical application and code compliance, this guide
is an invaluable asset for achieving a passing score and advancing one's career in plumbing.
Page 1
,Keywords:
Idaho Plumbing Code, Plumbing Exam Prep, Verified Questions, Rationales, 2026/2027 Edition, Licensure Exam,
Plumbing Systems, Code Compliance
Answer Format:
Each question is presented in a multiple-choice format with four options. The correct answer is clearly indicated,
followed by a comprehensive rationale that explains the underlying code section and reasoning. Distractor
explanations are also provided to clarify why the other options are incorrect, reinforcing learning and preventing
common misconceptions.
Compliance Checklist:
Aligned with the latest Idaho Plumbing Code (2026/2027)
All questions verified by subject matter experts
Rationales cite specific code sections for reference
Suitable for self-study and exam simulation
Instant download in PDF format for convenient access
Content Area Overview:
Content Area Questions Key Topics Weight
General Regulations and 1-10 Scope, Permits, Inspections, Enforcement 7%
Administration
Definitions and Terms 11-20 Key Terms, Abbreviations, Units 7%
Materials and Joints 21-35 Pipe Materials, Fittings, Joint Types, 10%
Installation
Sanitary Drainage Systems 36-55 Design, Sizing, Slope, Connections 13%
Venting Systems 56-70 Vent Types, Sizing, Installation, Venting 10%
Methods
Traps and Interceptors 71-80 Trap Types, Seal Protection, Interceptors 7%
Cleanouts and Access 81-90 Location, Sizing, Accessibility 7%
Water Supply and Distribution 91-110 Sizing, Pressure, Piping, Valves 13%
Hot Water Systems 111-120 Heaters, Safety Devices, Recirculation 7%
Plumbing Fixtures 121-130 Types, Installation, Accessibility, Efficiency 7%
Backflow Prevention 131-140 Cross-Connection, Devices, Testing 7%
Storm Drainage and Sewage 141-150 Storm Systems, Septic Tanks, Leach Fields 7%
Disposal
Page 2
,Q1. A five-story building has a sanitary stack receiving discharge from floor-mounted
water closets on floors 2-5. The stack is 4 inches in diameter and the total drainage
fixture units (DFU) connected is 320. The building drain is 6 inches. What is the
MINIMUM required continuous vent size for the sanitary stack, assuming the vent
connects to the stack at the top floor and extends to the roof?
A. 2 inches
B. 2-1/2 inches
C. 3 inches
D. 4 inches
Correct Answer: C. 3 inches
Rationale: Per IPC Table 916.1 (and Idaho amendments), the required continuous vent
size for a sanitary stack carrying 320 DFU with a 4-inch stack is 3 inches. A 2-inch or
2-1/2-inch vent is undersized for this load, and a 4-inch vent is not required.
Why Wrong:
A - 2 inches is only adequate for stacks up to 20 DFU in this configuration.
B - 2-1/2 inches is insufficient for the 320 DFU load.
D - 4 inches is larger than required; the code allows a smaller vent.
Reference: IPC 2018, Table 916.1; Idaho Amendments to IPC Chapter 9
Q2. A designer is specifying a backflow prevention assembly for a 3-inch irrigation
main connected to a public water supply. The irrigation system includes chemical
injection points. The water purveyor requires ASSE 1015 backflow prevention.
Which of the following is the MOST appropriate device and installation
consideration?
A. Double check valve assembly (DCVA) installed above grade with test cocks
B. Reduced pressure zone (RPZ) assembly with a 12-inch minimum clearance above
the flood rim
C. Atmospheric vacuum breaker (AVB) installed 6 inches above the highest outlet
D. Spill-resistant vacuum breaker (SVB) with a 12-inch clearance above grade
Correct Answer: B. Reduced pressure zone (RPZ) assembly with a 12-inch minimum
clearance above the flood rim
Rationale: Chemical injection creates a high-hazard backflow condition, requiring an
RPZ (ASSE 1015) to provide the highest level of protection. The RPZ must be installed
with adequate clearance for testing and maintenance, typically 12 inches above the flood
rim. A DCVA is not approved for high-hazard fluids, and vacuum breakers are not suitable
for continuous pressure or high-hazard applications.
Why Wrong:
A - DCVA is only acceptable for low-hazard (non-toxic) substances and would not
protect against chemical backflow.
Page 3
, C - AVB cannot be used under continuous pressure and is not rated for high-hazard
chemical backflow.
D - SVB is designed for high-hazard but is not a full RPZ and may not meet ASSE
1015 for this application.
Reference: IPC 2018, Section 608.13.5; ASSE 1015
Q3. A plumbing system has a horizontal wet vent serving a bathroom group
(lavatory, water closet, and shower) on a single floor. The wet vent is 2 inches in
diameter. What is the MAXIMUM drainage fixture unit (DFU) load that can be
served by this wet vent, and what is the required slope of the wet vent pipe?
A. 4 DFU, slope of 1/4 inch per foot
B. 4 DFU, slope of 1/8 inch per foot
C. 6 DFU, slope of 1/4 inch per foot
D. 6 DFU, slope of 1/8 inch per foot
Correct Answer: A. 4 DFU, slope of 1/4 inch per foot
Rationale: Per IPC Section 912.3, a 2-inch horizontal wet vent may serve up to 4 DFU
and must have a slope of 1/4 inch per foot (2% slope). The 6 DFU option exceeds the
allowable load, and 1/8 inch per foot is insufficient for a 2-inch pipe.
Why Wrong:
B - 1/8 inch per foot is too shallow for a 2-inch wet vent; code requires 1/4 inch per
foot.
C - 6 DFU exceeds the 4 DFU maximum for a 2-inch wet vent.
D - Both the DFU load and slope are incorrect.
Reference: IPC 2018, Section 912.3
Q4. In a commercial kitchen, a grease interceptor receives flow from
three-compartment sinks and a dishwasher. The interceptor is sized at 20 GPM.
According to the Idaho Plumbing Code, what is the MINIMUM capacity of the
interceptor in pounds of grease, and what is the required minimum flow rate through
the interceptor?
A. 20 pounds, 20 GPM
B. 20 pounds, 25 GPM
C. 40 pounds, 20 GPM
D. 40 pounds, 25 GPM
Correct Answer: B. 20 pounds, 25 GPM
Rationale: Idaho Plumbing Code requires grease interceptors to have a capacity of 2
pounds of grease per GPM of flow, and the flow rate must be at least the fixture discharge
rate. For a 20 GPM fixture discharge, the interceptor must handle 20 GPM and hold at
least 40 pounds of grease. Thus, the correct answer is 40 pounds and 20 GPM.
Page 4
