Journeyman Plumber Exam Prep

Exam blueprint

Sourced from IPC 2024 (ICC) + UPC (IAPMO) — Common State Journeyman Plumber Exam Outlines (PSI/Prov)

• Definitions + general regulations8%
• Fixture installation + clearances15%
• Traps + trap-arm rules12%
• DWV sizing (DFU + drain pipe sizing tables)15%
• Vent installation + sizing tables12%
• Water-supply rough-in + sizing tables12%
• Pipe materials + joining methods8%
• Pipe support + protection from damage6%
• Point-of-use backflow protection6%
• Pressure tests + inspection procedures6%

1. 01Fixture installation + clearances

   ~75min

   Where fixtures go, how much space they need, and the rough-in dimensions every journeyman commits to muscle memory.

   • Toilet + lavatory clearances — IPC 405.3.1

     Water closet clearance: 21" minimum from front of bowl to any wall, partition, or fixture per IPC 405.3.1; 30" minimum total clear width for the bowl (15" centerline to nearest side wall or fixture). UPC 402.5 requires 24" front clearance and 30" width — slightly different. ADA accessible water closets require 60" clear floor space (sidewall installations) or 56"-60" deep depending on configuration. Lavatories: 4" minimum from any wall on the back, 21" front clearance under IPC 405.3.1. The toilet centerline measurement is from the FINISHED wall, not the studs — set the closet flange at 12" rough from the finished wall (or 10" / 14" for older / oversized homes).

     Reference: IPC 2024 405.3.1

   • Rough-in heights + flange setting

     Standard rough-in heights from the finished floor: lavatory drain centerline 18-20" (per fixture rough-in spec); lavatory water supplies 21-23" with stops set to match; toilet flange ON TOP of finished floor (NEVER below — submerged flange leaks); toilet supply 8-1/2" off floor centerline ~6" left of bowl centerline; tub waste/overflow 5-1/4" up; tub spout 4" above tub flood-level rim with 28" overall valve set; shower head 80" from drain (residential standard). The toilet flange must sit ON the finished floor, sealed with a wax ring against the toilet. Setting the flange recessed below the floor causes EVERY toilet wax-ring failure long-term.

     Reference: IPC 2024 405.4

   • Maximum fixture flow rates — federal + code

     Federal Energy Policy Act (EPAct 1992) and IPC 604.4 limit maximum fixture flow rates: water closet ≤ 1.6 gpf (gallons per flush); urinal ≤ 1.0 gpf; private lavatory ≤ 2.2 gpm at 60 psi; public lavatory ≤ 0.5 gpm; showerhead ≤ 2.5 gpm at 80 psi; kitchen sink ≤ 2.2 gpm. WaterSense-labeled fixtures go below: 1.28 gpf toilet, 1.5 gpm aerator. Some states (California especially) impose tighter limits — CA Title 24: 1.28 gpf WC, 1.8 gpm shower, 1.2 gpm lav. Always check the project specs against the local code; the code mandates a CEILING, but the spec usually wants WaterSense or stricter.

     Reference: IPC 2024 604.4

   Practice questions (2)

   1. 1. Per IPC 405.3.1, the minimum clearance from the centerline of a water closet to any sidewall or partition is:

      • A.12 inches
      • B.15 inches✓ correct
      • C.18 inches
      • D.21 inches

      15 inches centerline-to-sidewall (IPC 405.3.1) — yielding 30" total width with a fixture/wall on each side. 12" is the toilet flange ROUGH from the finished wall, not the side clearance. 18" applies to an ADA accessible WC layout. 21" is the FRONT clearance from the bowl front to a wall or fixture. These four numbers are the most-confused journeyman trivia.

   2. 2. A toilet flange is installed 1/2 inch below the finished floor. Code-compliant?

      • A.Yes — ensures a tight seal
      • B.No — flange must be ON the finished floor✓ correct
      • C.Yes, with a double wax ring
      • D.Yes, if the floor is tile

      IPC 405.4 + manufacturer instructions: the closet flange sits ON the finished floor, not below. A recessed flange creates a hollow under the wax ring that compresses unevenly and eventually wicks sewage into the subfloor — the most common cause of rotted floors under toilets. Double wax rings are a band-aid that may pass inspection but masks a defective install. Floor finish material is irrelevant.

2. 02Traps + venting (installation rules)

   ~105min

   Every fixture has a trap; every trap has a vent. Trap-arm length, vent connection points, and the rules for individual / common / wet venting.

   • Trap-arm length — IPC 909

     TRAP ARM = the horizontal pipe between the trap weir and the vent connection. Maximum length per IPC Table 909.1: 1-1/4" trap arm = 5 ft; 1-1/2" = 6 ft; 2" = 8 ft; 3" = 12 ft; 4" = 16 ft. UPC Table 1002.2 has slightly different but similar limits. Vertical drop in the trap arm cannot exceed ONE PIPE DIAMETER (909.2) — measured from the trap weir to the lowest point of the vent fitting inlet. This rule prevents the arm from acting as a partial S-trap that self-siphons. TOO-LONG or TOO-DROPPED trap arms are the leading cause of dry-trap sewer-gas complaints in residential.

     Reference: IPC 2024 909.1, 909.2

   • Individual / common / wet venting

     INDIVIDUAL vent (901): one vent per trap, sized at half the drain it serves but ≥ 1-1/4". The default. COMMON vent (911): two fixtures back-to-back at the same level may share one vent — trap arms connect at a sanitary tee or double-Y on the vent's inlet. WET venting (912): a section of vent serves as drain for upstream fixtures in a bathroom group — IPC permits wet venting up to 4 fixtures including a water closet. The wet vent must be sized for total downstream DFU but at LEAST one pipe size larger than the largest connected trap arm. UPC restricts wet venting more tightly than IPC. CIRCUIT vent (913): used in commercial layouts with batteries of 2-8 floor-mounted fixtures.

     Reference: IPC 2024 911, 912, 913

   • Vent grade + connection rules

     Vents must rise from the drain at a grade that returns condensate to the drain (IPC 905.4) — typically 1/4" per foot back-grade is acceptable, but FLAT runs and back-pitched runs are violations. Vents connect to the drain via a sanitary tee or wye (IPC 905.3). The vent must rise vertically to AT LEAST 6" above the flood-level rim of the highest fixture served BEFORE running horizontal (IPC 905.4) — this prevents the vent from siphoning if a downstream fixture floods. Vent terminals through the roof: 6" above the roof; 12" above on a roof used for any purpose other than weather protection (IPC 904.1). 10 ft horizontally from any door, window, or air intake (904.5).

     Reference: IPC 2024 904, 905

   • Air admittance valves (AAVs) — when allowed

     AAVs are mechanical one-way valves that admit air into a vent system when negative pressure occurs (drainage in progress) and seal under positive pressure or atmospheric. Per IPC 918.6, AAVs may be used for individual, branch, or circuit vents — but NOT to vent sumps, sand interceptors, or to terminate a vent system. UPC has historically restricted AAVs heavily; many UPC jurisdictions only permit AAVs on islands, additions, or remodels where running a true vent is impossible. AAVs must be installed AT LEAST 4" above the highest horizontal drain branch and 6" above any insulation. Listed for the application (Studor, Oatey Sure-Vent are the dominant brands). DO NOT install AAVs in concealed locations without access — they require periodic replacement.

     Reference: IPC 2024 918

   Practice questions (3)

   1. 1. A 2" trap-arm serves a kitchen sink. Per IPC Table 909.1, the maximum length from trap weir to vent fitting is:

      • A.5 ft
      • B.6 ft
      • C.8 ft✓ correct
      • D.12 ft

      2" trap-arm max = 8 ft (IPC 909.1). 5 ft is the 1-1/4" limit. 6 ft is the 1-1/2" limit. 12 ft is the 3" limit. Memorize the table — these length limits scale with pipe size and are heavily tested. Exceeding the length forces a re-vent or moving the vent closer.

   2. 2. A vent rises from a horizontal drain branch and is to run horizontal. Per IPC 905.4, the vent must rise vertically at least how far above the flood-level rim of the highest fixture served?

      • A.1 inch
      • B.6 inches✓ correct
      • C.12 inches
      • D.24 inches

      6 inches above the flood-level rim before the vent may turn horizontal (IPC 905.4). Below this height, a flooded fixture could backflow into the vent and siphon adjacent traps. 1" is insufficient. 12" and 24" are sometimes used as project specs but are not the code minimum.

   3. 3. An air admittance valve (AAV) under IPC 918 may be used to vent:

      • A.A sump pump
      • B.An individual fixture or branch where a true vent cannot be installed✓ correct
      • C.The roof terminal of a vent stack
      • D.A sand or oil interceptor

      AAVs are permitted for individual fixture vents, branch vents, and circuit vents (IPC 918.3) — typically used when a true vent cannot be run, such as an island sink or a remodel. AAVs are PROHIBITED for venting sumps, interceptors, or as the building's primary vent terminal (a true atmospheric vent through the roof is still required). UPC restricts AAVs further than IPC; check the adopted code.

3. 03DWV sizing — DFU + drain pipe sizing

   ~90min

   Drain Fixture Units (DFU) drive everything. Match cumulative DFU to pipe size and slope per the code's tables.

   • Drain Fixture Units — IPC Table 709.1

     DFU values for common fixtures (IPC 709.1): water closet (private, 1.6 gpf) = 4 DFU; bathtub = 2; shower (single head) = 2; lavatory = 1; kitchen sink = 2; dishwasher = 2; clothes washer (residential) = 2; floor drain = 2; laundry tub = 2. UPC Table 702.1 differs slightly — UPC counts a private WC at 3 DFU and a bathtub at 2. Total DFU adds across all fixtures connected DOWNSTREAM of the pipe being sized. A typical 2-bath single-family home has ~30 DFU on the building drain. The DFU is a normalized "load unit" capturing both flow rate and use frequency — a fixture used briefly but at high flow (toilet) carries more DFU than one used continuously at low flow.

     Reference: IPC 2024 Table 709.1

   • Drain pipe sizing — IPC Table 710.1(2)

     Match cumulative DFU to drain size. IPC Table 710.1(2): horizontal branch 2" = 6 DFU max; 3" = 20 DFU; 4" = 160 DFU; 6" = 620 DFU. Building drain at 1/4" slope: 3" = 36 DFU; 4" = 216 DFU; 6" = 720 DFU. At 1/8" slope (4" and 6" pipes only): 4" = 180 DFU; 6" = 700 DFU. STACKS have separate columns — a 3" stack carries 60 DFU vs 35 DFU for a horizontal 3". Above 6 stories, stacks de-rate per 710.1(1) note. CRITICAL: a water closet REQUIRES at least a 3" drain — even though the 2" column would arithmetically allow a low-DFU branch with one. The fixture-specific minimum trumps the DFU table.

     Reference: IPC 2024 Table 710.1(2)

   • Drainage slope — IPC 704.1

     Standard minimum slope (IPC Table 704.1): pipe ≤ 2-1/2" = 1/4" per foot; pipe 3" or 4" = 1/8" per foot; pipe ≥ 6" = 1/16" per foot. Steeper slopes are allowed UP TO 1/2" per foot — beyond that, the flow self-strands solids and is a violation in many jurisdictions (IPC commentary). UPC permits 1/8" per foot only down to 4" pipe (UPC 708.1). Slope must be CONTINUOUS — sagged or back-pitched horizontal runs collect solids and produce stoppages. The slope is measured along the BOTTOM of the pipe, not the centerline; with copper or PVC, this is the same, but with cast iron and ductile iron the wall thickness matters at transitions.

     Reference: IPC 2024 704.1

   • Cleanout placement — IPC 708

     Cleanouts required (IPC 708.1): (1) at the upper terminal of every horizontal drain run; (2) at every change of direction greater than 45°; (3) at intervals not exceeding 100 ft for pipe larger than 4" or 50 ft for pipe 4" and smaller; (4) at the base of every vertical waste/soil stack; (5) at the building drain to building sewer junction (typically a 2-way cleanout outside the building wall). Cleanout SIZE matches the pipe up to 4"; for 5" and larger, a 4" cleanout is the minimum. Clearance: 18" in front of the cleanout for pipe 3" and larger, 12" for 2" and smaller (708.7). Cleanouts buried under finishes without an access plate fail inspection.

     Reference: IPC 2024 708

   Practice questions (2)

   1. 1. Per IPC Table 710.1(2), the maximum cumulative DFU on a 4" horizontal building drain at 1/4" per foot slope is:

      • A.96
      • B.160
      • C.216✓ correct
      • D.620

      4" at 1/4" slope = 216 DFU per IPC Table 710.1(2). 96 DFU is the 4" stack-only value (older editions). 160 is the 4" horizontal BRANCH limit (different column from the building drain). 620 is the 6" branch limit. The building-drain column accommodates more DFU than the branch column because the building drain has the steepest accumulating flow.

   2. 2. A horizontal 2" drain branch serves only a kitchen sink (2 DFU) and a dishwasher (2 DFU). May a single-occupancy water closet (4 DFU) be added downstream?

      • A.Yes — total DFU = 8 is under the 6 DFU limit for 2"
      • B.Yes, but only with an upgraded vent
      • C.No — water closets require minimum 3" drain regardless of DFU✓ correct
      • D.Yes, if the drain is sloped at 1/2" per foot

      IPC 710.1 + Table 709.2 fixture-specific minimums: a water closet REQUIRES a minimum 3" drain. Even though the DFU column might suggest a 2" pipe could carry the load, a fixture-specific minimum overrides. Slope and venting do not lift the WC drain-size minimum. This is a heavily-tested journeyman trap because the DFU arithmetic seems to permit it.

4. 04Water-supply rough-in + sizing

   ~75min

   Branch sizing tables, fixture supply minimums, and the rough-in dimensions for kitchen, bath, and laundry. Less full-system pressure budgeting (master) and more "what size pipe to this fixture".

   • Minimum fixture supply pipe size — IPC Table 604.5

     Minimum fixture-supply pipe size (IPC Table 604.5): water closet (tank) = 3/8"; flushometer WC = 1"; lavatory = 3/8"; bathtub = 1/2"; shower (single head) = 1/2"; kitchen sink = 1/2"; dishwasher = 3/8"; clothes washer = 1/2" (each hot/cold). UPC Table 610.20 differs — for example, UPC requires 1/2" minimum at lavatories. The supply minimum is the SHORT FLEXIBLE CONNECTOR or hard pipe directly serving the fixture; the BRANCH supplying multiple fixtures is sized larger per the WSFU + table approach. Most journeyman exams ask the fixture-supply minimum, not the full distribution sizing (which lives more on master exams).

     Reference: IPC 2024 Table 604.5

   • Rough-in supply heights + locations

     Standard rough-in: lavatory cold + hot stops 21-23" from finished floor (matched 8" apart center-to-center); kitchen sink stops 18-21" centered to spout; toilet supply 8-1/2" off floor, 6" left of bowl centerline; shower valve 48" centerline (or 38-44" for ADA); tub valve 28" with diverter spout 4" above tub flood-level rim; washer hookup 42" with hose bibbs and a standpipe at 18-30" (per local — typically 30" for new). Hose bibbs (sillcocks) outdoor at 12-18" above grade with frost-proof valves in cold climates. Run hot on the LEFT (at the user) and cold on the RIGHT — universal convention; flipping them at a faucet creates scald and customer-callback risk.

     Reference: IPC 2024 605.4 + manufacturer rough-in

   • Stops + isolation valves

     IPC 606.2: an accessible shutoff valve must be installed on the main water supply, on the supply to each water heater, and on each fixture's individual supply (the angle stop under a sink or behind a toilet). UPC 606.3 has matching requirements. The MAIN building shutoff is required and must be in an accessible location; gate valves and ball valves are both acceptable (modern best practice is full-port ball valves — quarter-turn, no slow gate-valve corrosion). Hose bibbs require a vacuum breaker (frost-proof exterior bibbs have integral atmospheric vacuum breakers); pressure-reducing valves are required when static pressure exceeds 80 psi (IPC 604.8). 80 psi is the upper limit for residential static pressure; above it, a PRV is mandatory.

     Reference: IPC 2024 604.8 + 606.2

   Practice questions (2)

   1. 1. Per IPC 604.8, when the static water pressure entering a building exceeds 80 psi, the installer must:

      • A.Install a check valve
      • B.Install a pressure-reducing valve (PRV)✓ correct
      • C.Increase pipe size by 1/2"
      • D.Add an air gap

      IPC 604.8 mandates a pressure-reducing valve (PRV) wherever static pressure exceeds 80 psi. Above that threshold, fixture trim and water-heater relief valves are subject to premature failure, and water-hammer becomes severe. A check valve prevents backflow but does not reduce pressure. Pipe size affects flow, not static pressure. Air gaps are for backflow, not pressure regulation.

   2. 2. Per IPC Table 604.5, the minimum fixture supply pipe size to a tank-type water closet is:

      • A.1/4"
      • B.3/8"✓ correct
      • C.1/2"
      • D.3/4"

      3/8" minimum supply to a tank-type WC (IPC Table 604.5). 1/4" is below code. 1/2" is required for showers, tubs, kitchen sinks. 3/4" is for hose bibbs and larger appliances. Note: a FLUSHOMETER WC requires 1" — not 3/8" — because flushometers draw flow during the flush rather than refilling slowly.

5. 05Tests, inspection, + pipe protection

   ~60min

   Pressure-test procedures, the rough-in inspection sequence, and the rules for protecting pipe from nails, freezing, and structural conflicts.

   • DWV + water test pressures

     IPC 312 — Tests + Inspections. DRAIN/VENT (DWV) ROUGH-IN: water test, 10 ft head MIN above the highest horizontal connection (or air test at 5 psi for 15 minutes). Pipe must hold without dropping. WATER SUPPLY ROUGH-IN: 50 psi minimum hydrostatic for at least 15 minutes; at least 100 psi for jurisdictions adopting tighter standards or where final operating pressure exceeds 80 psi. Some inspectors want the water-supply test to equal 1.5x the operating pressure. Building sewer (between cleanout-at-foundation and city main): 10 ft head test, no leakage. Document test results — many inspectors will not approve a rough-in without a pressure-test ticket.

     Reference: IPC 2024 312

   • Nail plates + bored hole protection

     IPC 305.6 (matches NEC 300.4): pipe within 1-1/4" of the edge of a wood stud or framing member must be protected by a STEEL NAIL PLATE at least 0.0625" (1/16") thick — typically a 1-1/2" x 5" galvanized "kick plate" nailed across the face of the stud. This protects against drywall screws and finish nails puncturing the pipe. Bored holes through wood framing must not exceed 60% of stud width in non-bearing partitions or 40% in bearing studs (IRC R602.6). Notches in studs are limited; many sole/top plates are notched but the notch must be sealed and protected. Drilled holes in joists similar limits per IRC.

     Reference: IPC 2024 305.6

   • Freeze protection — IPC 305.4

     IPC 305.4: water service pipe must be installed below the LOCAL FROST LINE (typically 30-48" in the Midwest, 12-24" in the South, 48-60" in the upper Midwest / Northeast). Building water-supply piping in unheated areas (attics, crawl spaces, exterior walls) requires insulation OR heat tape, OR the pipe is rerouted into conditioned space. Hose bibbs in freeze regions: frost-proof sillcocks (long stem with the shutoff inside the heated wall) — the routine "outdoor faucet drip" is no longer adequate code-side. Drain-down provisions for irrigation and exterior systems. Frozen pipes burst on THAW, not while frozen — the ice expands and ruptures the wall, but the burst point only releases water once liquid returns.

     Reference: IPC 2024 305.4

   Practice questions (2)

   1. 1. Per IPC 312, the minimum DWV water test for rough-in inspection is a head pressure of:

      • A.5 ft of water
      • B.10 ft of water above the highest horizontal connection✓ correct
      • C.50 psi
      • D.100 psi

      IPC 312.2 requires a water test of at least 10 ft of head above the highest horizontal joint; pipe must hold without dropping for the inspection period. 5 ft is insufficient for code. 50 and 100 psi are WATER-SUPPLY test pressures, not DWV. Air-test alternative is 5 psi but is not the water-test value.

   2. 2. A water line is run through a wood stud with the pipe edge 3/4" from the stud face. Per IPC 305.6, what additional protection is required?

      • A.None — 3/4" is acceptable
      • B.A 1/16" steel nail plate covering the area where the pipe is within 1-1/4" of the stud edge✓ correct
      • C.Insulation
      • D.Move pipe to the center of the stud

      IPC 305.6 + NEC 300.4 + IRC: any pipe within 1-1/4" of the stud edge requires a steel nail plate (≥ 1/16" thick) to deflect drywall screws and finish nails. 3/4" is well within the protected zone. Insulation alone does not stop nails. Re-routing might be ideal but a properly applied nail plate is code-compliant — most journeymen pull the plate from a strap of pre-cut pieces in the truck.

External resources

• Official
  International Plumbing Code (IPC) — current edition ↗

  ICC publishes the IPC online as a free read-only resource. For journeyman exam prep, focus on Chapters 3 (general regulations), 4 (fixtures), 6 (water supply), 7 (sanitary drainage), 8 (indirect waste), 9 (vents), and 10 (traps). These cover ~80% of journeyman-exam content.

• Official
  Uniform Plumbing Code (UPC) — IAPMO ↗

  IAPMO's UPC is the dominant code in the West. Differs from IPC on DFU values, vent rules, AAV permission, and graywater. If your state has adopted the UPC, study it — material from IPC will mislead you on key values.

• Third-party
  ICC Journeyman Plumber Exam Prep + Sample Questions ↗

  ICC publishes practice exams and exam-content outlines for the Journeyman Plumber certification (used by many states as the basis or as a parallel credential). Useful for practice-question style and to verify your understanding of code lookup speed.