Journeyman Plumbers Exam Cheat Sheet 2026

The 30 highest-yield Journeyman Plumbers Exam facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. What is the maximum vertical distance a fixture drain may drop before connecting to the trap arm? → The trap arm must be level or pitched to drain only
2. Combustion air for a gas-fired water heater in a confined space can be provided by: → Two permanent openings — one near the top and one near the bottom of the enclosure
3. On an isometric drawing, all measurements along the three isometric axes are drawn: → To true (actual) scale
4. Which of the following is the correct mathematical constant used to calculate the 'travel' piece when the 'set' of a 60-degree offset is known? → 1.155
5. Which of the following is an illegal and prohibited type of trap in a modern DWV system? → S-trap
6. Which fitting type is prohibited for use in a horizontal-to-horizontal drain change of direction? → Sanitary tee used on its side
7. A tankless (on-demand) water heater is rated primarily by: → BTU input and flow rate in gallons per minute
8. Which installation configuration is acceptable for a pressure vacuum breaker (PVB)? → Installed upstream of any chemical injection points
9. A sediment trap (drip leg) in a gas piping system must be installed: → Immediately upstream of each appliance
10. A plumber notices a gas odor while working in a building. The FIRST action should be: → Evacuate the building and call the gas company from outside
11. Which of the following joints is NOT acceptable for use in gas piping systems? → Solvent-cemented plastic pipe joints
12. Which venting category applies to a high-efficiency gas furnace with a flue gas temperature below 140°F and a positive vent pressure? → Category IV
13. What is the minimum diameter of the discharge pipe for a T&P relief valve on a residential storage water heater? → 3/4 inch
14. What substance is added to natural gas to give it its distinctive odor? → Mercaptan (ethyl mercaptan)
15. Which document primarily governs plumbing installations in most US jurisdictions? → International Plumbing Code (IPC) or Uniform Plumbing Code (UPC)
16. In isometric pipe drawing, how is a tee fitting typically shown when one branch comes toward the viewer? → As a line branching along the front 30-degree axis toward the viewer
17. Which formula correctly calculates the true length of a pipe in a rolling offset if the horizontal offset is H and the vertical rise is V? → True offset = √(H² + V²), then travel = true offset × offset constant
18. When sizing a gas piping system using the longest length method, what determines the pipe size for each section? → The longest supply length from meter to the farthest appliance
19. Which of the following locations is strictly prohibited for the installation of gas piping according to the International Fuel Gas Code? → Through a circulating air duct or chimney.
20. An isometric drawing shows a 60° offset on a 3-inch pipe. If the set (offset distance) is 9 inches, what is the approximate travel? → 10.4 inches
21. Cleanouts are required in a drainage system to allow for access. For a horizontal drainage pipe that is 100 feet long, where must cleanouts be located? → At the upper terminal and for each 100 feet, or fraction thereof, of developed length.
22. What is the correct location for a cleanout on a building drain near the foundation wall? → Outside the building, at the point where the drain exits the foundation
23. Based on the Uniform Plumbing Code (UPC), what is the maximum allowable developed length of the trap arm for a 1 1/2-inch P-trap? → 5 feet
24. The check valves inside a double check valve assembly (DCVA) must each be capable of holding against how much static pressure? → 10 psi
25. When connecting a clothes washer standpipe to the drainage system, the standpipe must extend at least how high above the trap? → 24 inches
26. According to the International Plumbing Code (IPC) and Uniform Plumbing Code (UPC), what is the acceptable range for a fixture trap's water seal depth? → 2 inches to 4 inches
27. Which of the following fixtures is assigned the highest drainage fixture unit (DFU) value under the IPC? → Water closet (flush tank)
28. A wet vent is permitted to serve which type of fixture combination? → Bathtub and lavatory on the same floor level
29. What is the minimum diameter for a vent pipe serving a 3-inch drain pipe under the IPC? → 1.5 inches
30. What is the minimum required diameter of a drain line from a water heater drain pan per most US plumbing codes? → 3/4 inch