Free Washington Journeyman Plumber Practice Test

Not quite. The answer is C: 4.5

Each private lavatory contributes 1.0 WSFU and the 1.6 gpf tank-type water closet contributes 2.5 WSFU in Table 610.3. Two lavatories plus one water closet is 1.0 + 1.0 + 2.5 = 4.5. The table lists one total value per fixture; a separate hot or cold share is only taken later, using the three-quarters allowance in the table's notes.

Not quite. The answer is B: 3

Table 702.1 rates a private-use 1.6 gpf gravity-tank water closet at 3 DFU; the same closet in public use is 4 DFU and in assembly use 6 DFU, and a closet using more than 1.6 gpf rates 4 DFU even in private use. The usual error is pulling the public or assembly column when the stem says private residence.

Not quite. The answer is C: 2 inch

A vent must be at least 1¼ inches and at least half the drain's diameter (1 inch here), so the floor is 1¼ inches — but load and length both govern. A 1½-inch vent is limited to 8 fixture units (and 60 feet), far short of 20 FU; a 2-inch vent is rated for 24 FU and 120 feet, which covers both the load and the 100-foot run. So 2 inches is the smallest vent that works.

Not quite. The answer is C: 24 inches

Washington's text of the UPC setting rule calls for 24 inches of clear space in front of a water closet or bidet, measured as a flat minimum. The 21-inch figure many candidates remember applies only inside dwelling units and sleeping units, where Washington allows the smaller clearance as an exception. The same section keeps water closets at least 15 inches from the center to a side wall or obstruction and 30 inches center to center.

Not quite. The answer is A: 6

Reading the isometric, the branch carries three private fixtures: a water closet (3 DFU), a lavatory (1 DFU) and a bathtub (2 DFU), for a total of 6 DFU. The drop sizes drawn (1½-inch, 3-inch, 2-inch) are fixture drain sizes, not numbers to add — the DFU value comes from the fixture-unit table, not from the pipe diameter on the drawing.

Not quite. The answer is B: Washington State Department of Labor & Industries (L&I)

Washington runs its plumbing certification program directly through L&I, which sets the requirements and contracts a testing vendor (PSI) for exam logistics — the content outline and licensing rules are the state's, not the vendor's or IAPMO's. ICC runs its own separate family of inspector certifications and has no role in Washington's journeyman licensing.

Not quite. The answer is B: 42 inches (3 feet 6 inches)

Table 1002.2 allows 42 inches — 3 feet 6 inches — of developed trap-arm length for a 1½-inch trap. The neighbouring rows are the usual wrong answers: 30 inches belongs to a 1¼-inch trap, 60 inches to a 2-inch trap and 72 inches to a 3-inch trap. The table also sets a minimum distance from the trap to the vent (3 inches for a 1½-inch trap).

Not quite. The answer is C: 6.5

Table 610.3 lists a single total per fixture — 1.0 for the private lavatory, 1.5 for the private kitchen sink and 4.0 for the bathtub — which adds to 6.5 WSFU. If a designer needs the hot-only load on a branch, the table's notes allow taking three-quarters of a fixture's listed total, but that is a calculation the designer performs, not a second number the table publishes.

Not quite. The answer is D: It may not be directly connected; potable makeup water to a non-pressurized storage tank is allowed only through an air gap

Gray water systems may have no direct connection to the potable supply (or to treated nonpotable or reclaimed water systems). The one allowance is makeup water for a non-pressurized storage tank, and then only through an air gap. Check valves and dual-check assemblies are not accepted substitutes, and filtering does not change that — this is a cross-connection rule, not a water-quality one.

Not quite. The answer is B: A connection between a potable water system and a source of actual or potential contamination

A cross-connection is any arrangement that could let non-potable water or another contaminant reach the potable system — a hose in a mop sink, a chemical feed line, an irrigation connection — not a description of a drain or vent fitting, terms it's easy for a new candidate to mix up with.

Not quite. The answer is B: 1 inch

Where the code calls for a drainage air gap, the vertical distance from the lowest point of the indirect waste pipe (or fixture outlet) to the flood-level rim of the receptor must be at least 1 inch. Do not confuse it with the water-supply air gap table, which scales with the faucet opening, or with the rule for potable water discharged to a drain, which is two pipe diameters but never under 1 inch. A trap on the receptor protects the drain side; it does nothing to stop the pipe itself from being submerged.

Not quite. The answer is A: Roof area (or projected horizontal area) and the local rainfall rate for the design storm

Storm drainage is a hydrology calculation, not a fixture-count calculation: leaders and drains are sized from the maximum projected roof area and the rainfall rate for the design storm (the UPC bases primary drainage on a 60-minute, 100-year storm unless the authority having jurisdiction says otherwise). DFU-based sanitary sizing measures a completely different quantity.

Not quite. The answer is B: 80 psi

Where static pressure in the water supply piping exceeds 80 psi, the code requires an approved pressure regulator (with a strainer ahead of it, unless the regulator is 1½ inches or larger) that brings the pressure down to 80 psi or less. An expansion tank is then required on the cold water side downstream of the regulator, because the regulator makes the system a closed one. Above 80 psi, fixtures, valves and the heater's relief setting wear out early.

Not quite. The answer is B: 6

Add the three table values: the private water closet is 3 DFU, the lavatory 1 DFU and the bathtub 2 DFU, for 6 DFU. The trap is treating the group as one lump value or mixing in the public-use column; on the exam you add each fixture from Table 702.1.

Not quite. The answer is B: 1.5 inch

The vent must be at least 1¼ inches and at least half the drain's diameter, so the floor is 1¼ inches. A 1¼-inch vent is rated for only 1 fixture unit, which is too small for 8 FU. A 1½-inch vent is rated for 8 FU and 60 feet, which covers both the load and the 40-foot run, so 1½ inches is the minimum — stepping up to 2 inches would work but is not required.

Not quite. The answer is C: 1.6 gallons per flush

In the 2015-edition Washington code the standard cap is 1.6 gallons per flush, matching the federal limit; 3.5 gpf appears only as an exception for day-care toilets, bedpan washers and blow-out bowls. The code Washington enforces on the job today is stricter: the 2021-edition Washington amendment (effective March 15, 2024) lowers the cap to 1.28 gpf and requires WaterSense-level performance. A plumber working from a current code book will see 1.28, so know which edition a question is asking about.

Not quite. The answer is B: Appropriately sized — 3 inches is the minimum for a branch carrying a water closet, and 6 DFU is well within a 3-inch drain's capacity

By load alone, 6 DFU would fit a 2-inch horizontal drain (rated 8 DFU), but the 2-inch row excludes water closets, and a water closet's minimum trap and trap arm is 3 inches. So 3 inches is the code minimum for this branch, and it is rated for 35 DFU — far above the 6 DFU load. The pipe is neither undersized nor oversized in a way a plan reviewer would mark.

Not quite. The answer is D: 8,000+ hours total, including 4,000+ hours commercial/industrial

Washington requires at least four years and 8,000 hours of documented trainee experience under a certified journey-level plumber, and half of that — at least 4,000 hours — has to be commercial or industrial work, so a candidate cannot qualify on residential-only experience. The 2,000-hour figure is the first-year direct-supervision requirement for a different certificate (residential service), which is the usual source of the mix-up.

Not quite. The answer is C: 60 inches (5 feet)

A 2-inch trap arm may run 60 inches — 5 feet — of developed length under Table 1002.2. The wrong answers are the neighbouring rows: 30 inches is the 1¼-inch limit, 42 inches the 1½-inch limit and 72 inches the 3-inch limit.

Not quite. The answer is B: Table 610.4 (Fixture Unit Table for Determining Water Pipe and Meter Sizes) — a separate table from the WSFU load values

Table 610.3 only assigns each fixture its WSFU load — it never converts that load into a pipe diameter. Actually sizing a pipe against a WSFU total, factoring in the available pressure range and the meter/building-supply size, is a separate table, 610.4. Reaching for 610.3 alone to size a pipe looks like the natural next step but doesn't contain a diameter answer at all.