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newSchoolWorks.com › VoTechWorks › Building & Construction › Plumbing & Pipefitting › Certification Exam Preparation: NCCER Plumbing L1–4, State Journeyman, and ASSE Backflow › Lesson 2
BLD-PLUM06-11 · Lesson 2 · 24 clock hours · theory

State Journeyman Licensing Exam: Code, Sizing, and Applied Trade Knowledge Review

Objective. Students will apply IPC and UPC code provisions, DWV and water-supply sizing methods, gas-piping requirements, and safety regulations to exam-style questions at the depth and format used on state journeyman licensing examinations.

What State Journeyman Licensing Exams Test

A state journeyman plumber license is a legal requirement to work in the trade without direct supervision. The written examination that precedes it is designed to confirm that you can apply plumbing codes and trade knowledge safely in real situations—not merely recall memorized facts. Most state exams are open-book for the adopted code (IPC or UPC, depending on the state), so your speed and accuracy in navigating the codebook directly affects your score.

Exam content typically spans several domains: plumbing codes and standards, water supply sizing and hydraulics, drain-waste-vent (DWV) design, venting requirements, water heater and backflow rules, gas piping basics, and safety regulations including OSHA requirements. Understanding what each domain demands—and where your gaps are—is the core purpose of this lesson.

Plumbing Codes: IPC and UPC

Most U.S. jurisdictions adopt either the International Plumbing Code (IPC), published by the International Code Council, or the Uniform Plumbing Code (UPC), published by the International Association of Plumbing and Mechanical Officials (IAPMO). A few states have state-specific codes that adopt one of these as a base. Know which code your state uses, because exam questions are written against that edition.

Both codes cover the same fundamental topics—materials, joints, fixtures, water supply, DWV, venting, traps, interceptors, water heaters, and fuel-gas basics—but differ in organization, fixture-unit values, and some sizing methods. When navigating either code under time pressure, use the table of contents and the index. Practice locating provisions quickly: water heater relief valve discharge requirements, maximum trap-to-vent distances, minimum fixture counts for occupancies, and trap seal depth are all common exam targets.

Fixture Units and DWV Sizing

Drainage fixture units (DFUs) are a standardized load measure assigned to each plumbing fixture. The code tables convert total DFU load into minimum pipe diameter for horizontal branches, stacks, and building drains. The method is consistent: count all fixtures on a branch or stack, sum the DFU values from the table, then read the minimum pipe size from the sizing table for the slope you are using (typically 1/4 inch per foot for horizontal drains).

For a building drain, you must also account for the number of branch intervals (floors) contributing to the stack. Stacks receiving soil or waste from more than three branch intervals use different column entries in the sizing table than shorter stacks—always check which column applies.

Venting protects trap seals from siphonage and back-pressure. Key venting provisions that appear on exams include: the maximum distance from a trap weir to the vent (the trap-to-vent distance, which varies by pipe diameter), the minimum diameter of individual vents, wet-vent applicability rules, and the point at which a vent must connect to a stack or outside air.

Water Supply Sizing and Hydraulics

Water supply sizing follows a fixture-unit method parallel to DWV but uses water supply fixture units (WSFUs). You sum fixture units for all outlets likely to operate simultaneously, apply a demand table to convert that sum to a design flow rate in gallons per minute, and then use friction-loss tables (or the Hazen-Williams method) to select a pipe size that delivers adequate pressure at the most remote or most demanding fixture.

Critical values to know: minimum static pressure required at fixtures, the pressure loss across a water meter, and the pressure drop per 100 feet of pipe at your design flow. Exam questions often give you a street pressure, a meter loss, an elevation change, and a pipe length, then ask for the residual pressure at a fixture or the minimum pipe size.

Water heater requirements frequently tested include: required temperature-and-pressure relief valves, proper discharge pipe routing (directed downward, terminating near the floor or to a safe location, never threaded at the end), minimum first-hour rating concepts, and expansion tank requirements when a backflow preventer creates a closed system.

Gas Piping Basics

Journeyman plumbing exams in states that include gas piping will test sizing of natural gas or LP gas piping using pressure-drop tables, identification of approved materials (such as black steel, CSST, and copper for LP in certain applications), prohibited materials, required shutoffs, and bonding and grounding of gas piping. Gas work carries serious life-safety implications: always treat any pressurized gas system as a potential ignition and asphyxiation hazard.

Safety: OSHA and Jobsite Hazards

OSHA regulations appear on nearly every state journeyman exam. Key topics include: fall protection thresholds for construction work, requirements for excavation and trenching (protective systems for trenches of regulated depth, competent-person inspections), personal protective equipment (eye, hand, respiratory, and foot protection), and hazard communication (safety data sheets and chemical labeling). Lockout/tagout (LOTO) procedures are critical whenever you work on systems that could be energized, pressurized, or released unexpectedly—de-energize, isolate, lock, tag, and verify before touching the system. Never skip LOTO steps under time pressure.

Exam Strategy

Open-book does not mean open-ended. You must locate answers faster than the clock. Build a personal index of the provisions you look up most slowly. On calculation questions, write down the formula, substitute values, and check units before computing—careless unit errors cause wrong answers on pipe-sizing questions. Tally your errors by domain after every practice set and target your weakest area first in review.

Key terms8

Drainage Fixture Unit (DFU)A unit of measure that represents the drainage load of a plumbing fixture; code tables use the total DFU count of a branch or stack to determine minimum pipe diameter.
Water Supply Fixture Unit (WSFU)A unit of measure representing the probable demand a fixture places on the water supply system; used with demand tables to find design flow rate in GPM.
Trap-to-Vent DistanceThe maximum allowable horizontal distance from the trap weir of a fixture to the point where the vent pipe connects; specified by code and varies with pipe diameter.
Temperature-and-Pressure (T&P) Relief ValveA safety device required on water heaters that opens automatically if water temperature or pressure exceeds set limits, preventing tank rupture.
Branch IntervalA vertical section of a plumbing stack, approximately one story in height, into which horizontal branches from fixtures connect; stack sizing depends on the number of branch intervals served.
Wet VentA pipe that serves simultaneously as both a drain for one fixture and a vent for another; permitted under specific code conditions regarding pipe size and fixture types.
Lockout/Tagout (LOTO)An OSHA-required procedure to de-energize and physically isolate equipment—electrical, pneumatic, hydraulic, or pressurized—before performing maintenance or service, protecting workers from unexpected release of energy.
Hazen-Williams MethodA widely used hydraulic formula for calculating friction-loss in water supply piping, relating flow rate, pipe diameter, pipe material roughness coefficient, and pressure drop per unit length.

Worked examples4

1. A horizontal drain branch at 1/4-inch-per-foot slope serves the following fixtures: one toilet (water closet), one lavatory, and one bathtub. Using a standard IPC-style DFU table where a water closet = 4 DFU, lavatory = 1 DFU, and bathtub = 2 DFU, what is the minimum diameter for that branch?
  1. Step 1 – Sum the DFU values: toilet 4 + lavatory 1 + bathtub 2 = 7 DFU total.
  2. Step 2 – Go to the horizontal-fixture-branch sizing table for 1/4-inch-per-foot slope. A 2-inch pipe handles up to 3 DFU on a branch; a 3-inch pipe handles up to 20 DFU (and receives the water closet, which alone requires a minimum 3-inch connection).
  3. Step 3 – Confirm the water closet requires a minimum 3-inch connection regardless of total DFU. Because the toilet is present and total DFU is 7, a 3-inch branch satisfies both rules.
  4. Step 4 – State the answer with code basis: minimum 3-inch diameter, governed by both the DFU total and the individual fixture minimum for a water closet.
Answer: 3-inch diameter minimum for the horizontal branch.
2. A water main supplies 65 psi at the meter. The meter pressure loss is 5 psi. The most remote fixture is 18 feet above the meter (elevation pressure loss = 0.433 psi per foot of rise). Friction loss in the piping is 8 psi. What is the estimated residual pressure at the remote fixture?
  1. Step 1 – Identify all pressure losses: meter loss = 5 psi; elevation loss = 18 ft × 0.433 psi/ft = 7.794 psi, round to 7.8 psi; friction loss = 8 psi.
  2. Step 2 – Sum all losses: 5 + 7.8 + 8 = 20.8 psi total loss.
  3. Step 3 – Subtract total loss from supply pressure: 65 − 20.8 = 44.2 psi residual at the remote fixture.
  4. Step 4 – Compare to the code minimum (commonly 15–20 psi for most fixtures under the IPC); 44.2 psi exceeds that minimum, so the system is adequate.
Answer: Approximately 44.2 psi residual pressure at the remote fixture.
3. A plumbing stack serves five branch intervals in a residential building. The total DFU load on the stack is 90 DFU. Using a standard IPC-style stack sizing table (stacks with more than three branch intervals), what is the minimum stack diameter?
  1. Step 1 – Confirm which column applies: five branch intervals is more than three, so use the 'more than three branch intervals' column of the stack sizing table.
  2. Step 2 – Read the table: a 3-inch stack (more than three intervals column) handles up to 48 DFU; a 4-inch stack handles up to 240 DFU.
  3. Step 3 – Compare: 90 DFU exceeds the 3-inch limit (48 DFU) but is within the 4-inch limit (240 DFU).
  4. Step 4 – Select minimum stack size and note the code basis: 4-inch diameter stack, sized from the stack table for more than three branch intervals.
Answer: 4-inch diameter minimum for the stack.
4. A T&P relief valve on a water heater discharges through a relief valve discharge pipe. The pipe is 3/4-inch diameter and runs 6 feet horizontally then 4 feet vertically downward to terminate 6 inches above a floor drain. Identify two code-required features that must be verified for this installation.
  1. Step 1 – Verify termination height: the discharge pipe must terminate between 6 inches and the floor level above a drain, pointing downward—6 inches above the floor drain is correct.
  2. Step 2 – Verify the pipe end is not threaded or capped: the discharge outlet must be open (not threaded, valved, or plugged) so pressure cannot be trapped.
  3. Step 3 – Verify pipe material is approved for the discharge temperature (relief valve discharge can reach near boiling); materials must be rated for high temperature.
  4. Step 4 – Verify no intervening shutoff valve is installed in the discharge line; a valve could prevent the relief valve from operating properly—this is prohibited by code.
Answer: Two required features: (1) discharge pipe terminates pointing downward, 6 inches above the floor drain with an open, unthreaded end; (2) no shutoff valve is installed anywhere in the discharge pipe.

The math in this lesson2

Learners total DFU loads for a bathroom group to size a horizontal branch.
7.NS.3A-SSE.1
Brush up in the math halls at newSchoolWorks.com:
In class: Instructor presents the typical content domains of state journeyman plumber written exams—plumbing codes, pipe sizing and hydraulics, fixture units, venting, water heater and water supply requirements, gas piping basics, and safety/OSHA—and leads a code-book navigation drill in which students race to locate and cite specific provisions (water heater relief valve requirements, trap-to-vent distances, minimum fixture counts) using their IPC or UPC reference; students record the code section and plain-language meaning for each item. · Students complete a 40-question timed practice set in exam format (no notes except the codebook), then grade their own papers using an answer key, tally errors by domain, and enter results into their personal tracking sheet to update their gap analysis. · Small groups are assigned a realistic plumbing scenario (e.g., sizing a DWV system for a three-story apartment building or calculating minimum pipe diameter for a given fixture-unit load) and must produce a written solution citing the applicable code section; groups present their solution to the class for peer critique and instructor correction.
Materials: IPC and UPC codebooks (current edition used in the program), instructor-prepared journeyman-style practice question bank, answer keys, personal score-tracking sheet, calculator, friction-loss and fixture-unit tables from program coursework
Check: Students score 70% or higher on the 40-question timed practice set; any student below 70% on any identified domain is assigned a specific reading and practice-problem set from course 2 (IPC/UPC Codes) and course 3 (DWV) materials to complete before Lesson 4.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

DWV and Venting
1. Under the IPC, a trap installed on a 2-inch drain pipe must connect to a vent within what maximum horizontal distance from the trap weir?
Water Heater and Water Supply
2. A water heater temperature-and-pressure relief valve discharge pipe must terminate:
DWV Sizing
3. When sizing a building drain to carry the combined load of multiple stacks and branches, the plumber must account for which of the following in addition to total DFU load?
Safety and OSHA
4. Before cutting into a pressurized water supply line inside a wall, OSHA and safe trade practice require the worker to:
DWV Sizing
5. A three-story apartment building has a soil stack receiving waste from three floors. The total DFU load on the stack is 55 DFU. The designer initially sized the stack at 3 inches. Why is this likely incorrect?
Gas Piping
6. Which of the following pipe materials is generally NOT approved for use as a natural gas distribution piping inside a building under most U.S. codes?
Water Supply Sizing and Hydraulics
7. Using water supply fixture units (WSFUs) and a demand table, a plumber calculates a design flow rate of 28 GPM for a building's cold-water main. The street pressure is 60 psi. Total pressure losses (meter, elevation, friction) sum to 22 psi. What is the estimated residual pressure at the critical fixture?
Safety and OSHA
8. A journeyman plumber is working in a trench that is 6 feet deep with vertical walls and no shoring. Under OSHA excavation standards, this situation:
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