Idaho Plumbing Journeyman Exam Practice Exam
Outline update: PSI's Idaho candidate information bulletin effective July 9, 2026 restructured this exam. The 100 questions now cover the 2015 Uniform Plumbing Code, Chapters 3 through 12 (75 questions), plus a 25-question section on Idaho's amendments to that code as printed in the 2017 Idaho State Plumbing Code. Chapters 1, 2 and 13 through 17 are no longer listed, and the two schematic sizing questions were removed. Either the 2015 UPC or the 2017 ISPC may be brought into the test center (open book).
This practice exam was rebuilt to the new outline on September 14, 2026.
Free Practice Exam
Test your knowledge with 10 questions from our pool of 20 free questions.
- 10 questions per attempt
- 30 minute time limit
- Unlimited attempts
- A new mix each time
- Instant results
Full Practice Exam
Complete exam simulation matching the real PSI test format.
- 100 questions (same as real exam)
- 180 minute time limit
- 11 topic areas covered
- 430 questions in pool
- Detailed explanations
Texts preferred · 9am–9pm Central
Idaho Plumbing Journeyman Exam Practice Exam Guide
What's on the exam
Questions per topic, out of 100The Idaho Plumbing Journeyman Exam is open book, and it is built on the 2015 Uniform Plumbing Code and the 2017 Idaho State Plumbing Code. The outline runs from material standards and pipe protection in Chapter 3 through fixtures, water heaters, water supply, drainage, indirect waste, venting, traps and interceptors, storm drainage and fuel gas piping. The largest single block is the 2017 Idaho State Plumbing amendments, at 25 items.
You have two ways to practice here. The free practice exam gives you 10 questions per attempt, and you can retake it as often as you like. The full practice exam gives you 100 questions on a 3 hours clock, drawn fresh from our question bank every time you start it, so repeat attempts do not turn into memorizing a fixed list. Both come with the answer, the reasoning and the code section behind it.
2015 Uniform Plumbing Code Chapter 3 6 items
This chapter covers material standards, prohibited fittings, protecting and supporting pipe, trenching, alternate materials, flood hazard areas and test gauges. Expect UV protection for PVC exposed to sunlight — wrapping with tape not less than 0.04 inch thick is acceptable, oil-based paint is not (2017 ISPC Section 312.14). You will also see connections of dissimilar metals confined to exposed or accessible locations (2017 ISPC Section 310.6), the provisions for soil and drain pipe run over food-handling areas, including cleanouts extended through the floor above (2017 ISPC Section 317.1), and trenching details such as tunnel clear height above the pipe (2017 ISPC, Section 314.2).
2015 Uniform Plumbing Code Chapter 4 8 items
Fixture questions split between counts and numbers. Know the single-unisex-facility exceptions by occupant load for small occupancies and for business and mercantile occupancies (2017 ISPC Section 422.2, Exception (2) and 2017 ISPC Section 422.2, Exception (3)). Know the clear space in front of a water closet, lavatory or bidet (2017 ISPC Section 402.5). Flow and consumption limits come up straight: showerhead maximum flow rate at 80 psi (2017 ISPC Section 408.2) and maximum water closet consumption per flush (2017 ISPC Section 411.2). Memorize those three numbers cold.
2015 Uniform Plumbing Code Chapter 5 4 items
Only four items, and the practice questions for this chapter ask for numbers you either know or look up fast. Unlisted water heater clearance on all sides and rear is in 2017 ISPC Section 504.3.2. Attic and overflow protection — pan depth and drain size — is 2017 ISPC Section 507.5. The rest is combustion air math: the standard method volume per 1,000 Btu/h (2017 ISPC Section 506.2.1) and free area per Btu/h for two permanent openings through horizontal ducts to the outdoors (2017 ISPC Section 506.4.1(2)).
2015 Uniform Plumbing Code Chapter 6 8 items
Water supply and backflow. Identification questions ask the potable color scheme (2017 ISPC Section 601.3.1) and how often nonpotable markings repeat (2017 ISPC Section 601.3.2). Material questions ask maximum lead content in solder and flux for water for human consumption (2017 ISPC Section 604.2) and the length of piping at a water heater where PEX, PEX-AL-PEX, PE-AL-PE or PE-RT is not permitted (2017 ISPC Section 604.13). Backflow assembly access shows up as clearance between the lowest portion of the assembly and grade, floor or platform (2017 ISPC Section 603.4.3).
2015 Uniform Plumbing Code Chapter 7 9 items
Drainage is a heavy topic. Expect approved fittings where a horizontal line enters a vertical stack, and which fitting is not approved (2017 ISPC Section 706.2). Expect backwater valve protection where fixtures sit below the next upstream manhole cover (2017 ISPC Section 710.1), and sump-and-ejector requirements where fixtures sit below the crown level of the main sewer (2017 ISPC Section 710.2). Material restrictions on galvanized wrought-iron and galvanized steel underground appear in 2017 ISPC, Section 701.2(1). Minimum uniform slope for horizontal drainage piping is 2017 ISPC Section 708.1.
2015 Uniform Plumbing Code Chapter 8 4 items
Indirect waste. Know the minimum vertical distance for a drainage air gap measured from the lowest point of the indirect waste pipe to the flood-level rim (2017 ISPC Section 801.2). Know that indirect waste pipes over 5 feet but less than 15 feet are directly trapped and those traps need not be vented (2017 ISPC Section 803.3). Water softener drain questions ask minimum line size and where the drain may terminate (2017 ISPC Section 805.1). Condensate questions ask acceptable overflow protection for equipment above finished space (2017 ISPC Section 814.2).
2015 Uniform Plumbing Code Chapter 9 9 items
Venting is another heavy topic. Island sink venting — how high the vent goes, drainage fittings below floor, and what the upstream drain may serve — comes from 2017 ISPC Section 909.1. Combination waste and vent questions ask what happens to a branch over 15 feet (2017 ISPC Section 910.3). Sizing basics: minimum diameter of an individual vent relative to the drain (2017 ISPC Section 904.1). Design and terminal rules: maximum pressure differential on the outlet side of a trap seal (2017 ISPC Section 901.3) and terminal size where frost closure is likely (2017 ISPC Section 906.7).
2015 Uniform Plumbing Code Chapter 10 5 items
Traps and interceptors. A commercial sink question asks how a food waste disposer installed with restaurant, commercial or industrial sinks must be trapped (2017 ISPC Section 1001.2). Trap arm questions send you to 2017 ISPC Table 1002.2 for maximum developed length by trap arm size — read the row, do not guess. Prohibited trap types are listed in 2017 ISPC Section 1004.1, and fixture trap liquid seal depth, minimum and maximum, in 2017 ISPC Section 1005.1.
2015 Uniform Plumbing Code Chapter 11 10 items
Storm drainage carries ten items. Start with the flat prohibition on draining storm water into sewers intended for sanitary drainage (2017 ISPC Section 1101.3). Subsoil drainage questions cover minimum pipe diameter and bedding (2017 ISPC Section 1101.6), sump pump capacity and sump size (2017 ISPC Section 1101.6.2), piping continuously flowing springs or groundwater to a storm drain or approved water course (2017 ISPC Sections 1101.6.1 and 1101.6.3), and discharge distance from a property line (2017 ISPC Section 1101.6.5). Trapping of leaders and storm drains connected to a combined sewer is 2017 ISPC Section 1101.15.
2015 Uniform Plumbing Code Chapter 12 12 items
The biggest UPC block. Know the pressure the chapter governs up to (2017 ISPC Section 1201.1). Inspection questions cover excavations kept open and piping exposed on direction of the Authority Having Jurisdiction (2017 ISPC Section 1203.2). Sizing questions ask what to do when existing piping may be inadequate for an added appliance (2017 ISPC Section 1208.1.1). Materials: the prohibited metallic pipe (2017 ISPC Section 1208.5.2) and brazing melting point for nonferrous pipe (2017 ISPC Section 1208.5.8.1). Underground work: minimum cover (2017 ISPC Section 1210.1.1) and tracer wire size with plastic pipe (2017 ISPC Section 1210.1.7.2).
2017 Idaho State Plumbing 25 items
One quarter of the exam is Idaho's amendments, so learn where they differ. Our practice questions here cover trap seal primers for infrequently used floor drains (2017 ISPC Section 1007.1), shower receptor floor slope (2017 ISPC Section 408.5), Category 3 or 4 vent air testing (2017 ISPC Section 503.1), 18-inch ignition-source height in residential garages (2017 ISPC Section 507.13), minimum 2-inch underground drain and vent (2017 ISPC Section 703.1), double sanitary tee barrel size (2017 ISPC Section 704.2), cleanout intervals (2017 ISPC Section 707.4), frost-proof hose bibbs (2017 ISPC, Section 603.5.7), backflow assembly testing schedule (2017 ISPC Section 603.4.2), dishwasher connections (2017 ISPC Section 807.3) and AAV limits (2017 ISPC Section 909.1(a), 2017 ISPC Section 909.1(b)).
Sample 1 — 2017 Idaho State Plumbing
Question: You are working on a commercial building where there are several floor drains connected to the drainage system that are seldom used. The building owner asks if any additional protection is needed for these drains. According to the 2017 ISPC, what is required?
- A. No additional protection is needed as long as the traps have a 2-inch liquid seal
- B. The drains must be capped off if they are not used regularly
- C. The drains shall be protected with a trap seal primer or other approved trap seal protection device
- D. The drains must be connected to a separate venting system to prevent siphonage
Correct Answer: C
Floor drains or similar traps directly connected to the drainage system and subject to infrequent use must be protected with a trap seal primer or other approved trap seal protection device. The only relief is where the Authority Having Jurisdiction does not deem it necessary for safety or sanitation. Trap seal primers also have to be accessible for maintenance. Citation: 2017 ISPC Section 1007.1.
Sample 2 — 2015 Uniform Plumbing Code Chapter 12
Question: You are installing a new gas furnace in a residential home and need to connect to the existing gas piping system. Upon evaluation, you determine the existing piping may be undersized for the additional load. According to the 2017 ISPC, what must you do?
- A. Install the appliance and adjust the gas pressure regulator to compensate
- B. Check the existing piping for adequate capacity and enlarge the system if inadequate, or provide a separate gas piping system of approved capacity
- C. Reduce the input rating of the new furnace to match the existing piping capacity
- D. Install a booster pump on the existing gas line to increase flow
Correct Answer: B
Where additional appliances are connected to a gas piping system, the existing piping has to be checked for adequate capacity. If it is inadequate, you enlarge the existing system or run separate gas piping of approved capacity. The code puts the burden on verifying capacity first, then correcting the piping — not on adjusting equipment or pressure to work around undersized pipe. Citation: 2017 ISPC Section 1208.1.1.
Sample 3 — 2015 Uniform Plumbing Code Chapter 11
Question: You are a journeyman plumber installing a subsoil drain system around a new residential basement. The homeowner asks if the drain can discharge onto the lawn 8 feet from the property line since there is no storm drain available. What should you tell them?
- A. This is acceptable as long as water flows away from the building
- B. This is not permitted because subsoil drains must always connect to a storm drain
- C. This is acceptable as long as a backwater valve is installed
- D. This is not permitted because the discharge point must be at least 10 feet from a property line
Correct Answer: D
Drains discharging to a properly graded open area must have the point of discharge not less than 10 feet from a property line. At 8 feet the installation does not comply. Note that option B overstates the rule — the code provides for drains discharging to a properly graded open area, with the point of discharge not less than 10 feet from a property line, although continuously flowing springs or groundwater must be piped to a storm drain or an approved water course (2017 ISPC Sections 1101.6.1 and 1101.6.3). Read distance questions for the exact measured point. Citation: 2017 ISPC Section 1101.6.5.
The real exam is scored at a minimum score of 70. Use that as your line, but do not read your first practice score as a prediction. Treat attempt one as a diagnostic. It tells you two things: whether you can find answers in your code book fast enough, and which chapters you are guessing in.
The topic breakdown matters more than the total. A 72% that is built on weak Chapter 9 and weak Idaho amendments is more fragile than a 68% spread evenly, because the Idaho amendments are the largest topic at 25 items and Chapter 9 carries 9. Work from the outline counts. The 2017 Idaho State Plumbing amendments are 25 items, Chapter 12 is 12, Chapter 11 is 10, and Chapters 7 and 9 are 9 each. That is 65 of the scored items in five topics. Gains there move your total the most.
Retake the full practice exam under the clock, not open-ended. You get a fresh draw each attempt, so a rising score across attempts means you actually know the material rather than the item. When you miss one, go to the cited section in your book and read it.
Answering from memory instead of the book. This exam is open book, and the questions reward looking things up. Trap arm length questions send you to 2017 ISPC Table 1002.2 — the answer is a row in the table. Same with combustion air sizing under 2017 ISPC Section 506.4.1(2): the free-area ratio is stated in the section, so look it up instead of recalling it.
Missing the Idaho amendment. The heaviest topic is the amendments, at 25 items, so learn where Idaho differs from the unamended UPC rule. Double sanitary tee barrel sizing under 2017 ISPC Section 704.2 is a good example: the general stack-connection rule would increase the barrel, but 2-inch and smaller double sanitary tees used for back-to-back or side-by-side fixture trap arms do not require it.
Over-broad "always" and "never" thinking. Subsoil drains do not always have to connect to a storm drain: 2017 ISPC Section 1101.6.5 provides for drains discharging to a properly graded open area, with the point of discharge not less than 10 feet from a property line, although continuously flowing springs or groundwater must be piped to a storm drain or an approved water course (2017 ISPC Sections 1101.6.1 and 1101.6.3). AAV rules are not blanket bans either: 2017 ISPC Section 909.1(a) and 2017 ISPC Section 909.1(b) set specific limits. When an option says always, check the exception first.
Skipping the qualifier in the scenario. In Chapter 7, whether you need a backwater valve (2017 ISPC Section 710.1) or a sump and ejector (2017 ISPC Section 710.2) depends on which reference elevation the stem gives you — the next upstream manhole cover, or the crown level of the main sewer. Read that line twice.
Losing time on lookups. With 3 hours for 100 questions, your pace is about 1 minute 48 seconds per question. Anything you have to hunt for blind costs you time on questions elsewhere.
| Questions | 100 questions |
| Time limit | 3 hours |
| Passing score | a minimum score of 70 |
| Books in the exam room | Open book |
| Exam fee | $75 |
- Your score is shown on screen at the end of the exam and a score report is provided, with a diagnostic report of strengths and weaknesses if you fail.
- If you do not pass, you may retake the exam as many times as needed, paying an examination fee for each attempt.
Source: Examination Scheduling Procedures / Examination Guide (Idaho PSI Candidate Bulletin), Effective 7/9/2026. Check the bulletin before test day: fees and rules can change.