Free Master Plumber Practice Test

Answer: B. 216 DFU
Table 710.1(1) rates a 4-inch building drain at 180 DFU at ⅛ in/ft, 216 at ¼ in/ft and 250 at ½ in/ft. More slope means more capacity from the same pipe, so read the column for the slope you're installing. 180 is the ⅛ in/ft figure and 250 the ½ in/ft figure. 840 is the 6-inch drain at ¼ in/ft, which means the wrong row.
Look up: IPC Table 710.1(1).
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: C. 6 inch
At ⅛ in/ft, Table 710.1(1) allows 36 DFU on a 3-inch drain, 180 on a 4-inch and 700 on a 6-inch. 200 DFU is more than the 4-inch limit, so 4-inch fails at this slope even though it would pass at ¼ in/ft (216). 6-inch is the smallest size listed that carries the load. 8-inch works but isn't the smallest.
Look up: IPC Table 710.1(1).
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: C. ¼ inch per foot
At ⅛ in/ft a 4-inch building drain is rated for 180 DFU, short of 200. At ¼ in/ft it's rated for 216, which covers the load. The table gives no 1/16 in/ft rating for 4-inch pipe at all. ½ in/ft works too, but it isn't the minimum. This is the previous question turned around: master exams ask you to solve for size or for slope from the same table.
Look up: IPC Table 710.1(1).
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: B. 3 inch
A footnote to Table 710.1(1) sets 3 inches as the minimum for any building drain serving a water closet, no matter how few DFU it carries. 2-inch is too small even for a single toilet. 4-inch is a common job-site choice, but it isn't the code minimum, and 6-inch is a design choice for large loads.
Look up: IPC Table 710.1(1), footnote a.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: B. 20 DFU
Table 710.1(2) limits a 3-inch horizontal fixture branch to 20 DFU. 48 is the limit for a 3-inch stack of three branch intervals or fewer, so it comes from reading the stack column instead of the branch column. 6 is the 2-inch branch limit and 160 is the 4-inch branch limit.
Look up: IPC Table 710.1(2).
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: D. 18 inches in diameter and 24 inches deep
The pit must be at least 18 inches in diameter and 24 inches deep. The other three choices each fall short on diameter, depth or both. The same section also requires a gastight removable cover and a vent that meets Chapter 9, because a sealed sewage pit still needs air.
Look up: IPC 712.3.2.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: D. 2 inches
Pumps that receive water closet discharge must pass 2-inch spherical solids. ½ inch is the requirement for pumps that don't receive water closets, so it's the trap answer here. 1 inch and 1½ inches aren't the code's figures. Grinder pumps and macerating toilets have their own exceptions in the same section.
Look up: IPC 712.4.2.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: D. Through a wye fitting into the top of the drain, at least 10 pipe diameters from the base of any stack
Pumped flow enters from the top through a wye, so it joins the gravity flow without backing it up. Keeping 10 pipe diameters away from the base of a stack keeps it out of the turbulent zone where the stack turns horizontal. A side or bottom entry, or a connection at the stack base, puts pumped flow where it fights the gravity flow.
Look up: IPC 712.3.5.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: A. Five or more
Five or more branch intervals triggers a vent stack. A branch interval is a vertical stretch of stack, at least 8 ft, where horizontal branches connect. 'More than 10' is the separate trigger for relief vents (next question), which is why the two numbers get swapped. Eight isn't a trigger at all; it's the minimum height of one branch interval.
Look up: IPC 904.2.
Source: ICC Building Safety Journal: venting methods in the 2021 IPC · 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: C. 10
In buildings with more than 10 branch intervals, stacks need relief vents to balance pressure along that height. 5 is the vent-stack trigger from the previous question, 8 is the minimum height of a branch interval in feet, and 15 isn't a code threshold.
Look up: IPC 908.1.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: D. At least 3 inches in diameter, with any size increase made at least 1 foot inside the thermal envelope
Frost-closure protection requires vent extensions of at least 3 inches. Any increase in size must start at least 1 foot inside the thermal envelope, where the pipe is still warm, so frost can't build up at a reducer in cold air. Options that put the increase at or above the roof, or outside the envelope, put the reducer where it can freeze shut. The rule applies where the 97.5% design temperature is 0°F or lower.
Look up: IPC 903.2.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: C. 6 inches
At least 6 inches. If the drain backs up, waste then can't run into the horizontal vent and block it. 2 and 4 inches leave too little margin, and 12 inches is more than the code asks.
Look up: IPC 905.4.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: A. ¾ inch
The water service must be at least ¾ inch. Larger sizes come from the design calculation for the building's demand, so 1 inch and up are common results but not the code minimum.
Look up: IPC 603.1.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: A. The bottom of the water service is at least 12 inches above the top of the building sewer
The default rule is 5 feet of horizontal separation in undisturbed or compacted earth. Closer is allowed only if the sewer is a Table 702.2 material, the water service is sleeved at a crossing, or the bottom of the water service is at least 12 inches above the top of the sewer. 6 inches above isn't enough, and 3 feet apart is less than the 5 feet required. Running the water line below the sewer is the worst choice, because a leaking sewer drains toward it.
Look up: IPC 603.2.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org) · Ohio Plumbing Code rule 4101:3-6-01 (2021 IPC-based)

Answer: B. 50 feet
The IPC limits this to 50 feet. Beyond that you need a circulating system or heat-trace piping so users don't wait for hot water. 100 feet is the IRC's residential figure, which is the usual trap for candidates who study both codes. 25 and 75 feet aren't code figures. In the 2024 edition the circulation and heat-trace subsection moves from 607.2.1 to 607.2.2.
Look up: IPC 607.2.
Source: 2012 IPC text (Public.Resource.Org) · 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org) · ICC 2024 IPC significant changes (EduCode session)

Answer: B. 110°F
Tempered water from an ASSE 1070 (also ASME A112.1070/CSA B125.70) device must be set no higher than 110°F. 120°F is the limit for bathtub and whirlpool fillers, a different provision for different fixtures. 100°F is below the limit, and 140°F is a water heater storage temperature, not a delivery limit.
Look up: IPC 607.1.2; public hand-washing provision in Chapter 4 (419.5 in 2021).
Source: ICC Building Safety Journal: hot water safety

Answer: C. A thermal expansion control device downstream of the pressure-reducing valve, sized per the manufacturer
A check valve, PRV or backflow preventer on the cold supply closes the system. When water heats and expands, pressure has nowhere to go, so the code requires a thermal expansion control device (typically an expansion tank) on the heater side of those devices. It must be sized so pressure stays within the IPC's maximum pressure limit (604.8). Relying on the relief valve to drip every heating cycle doesn't comply. A vacuum relief valve or a second PRV doesn't give the expanding water anywhere to go.
Look up: IPC 607.3.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: D. 0.5 gpm at 60 psi
Table 604.4 limits public, non-metering lavatory faucets to 0.5 gpm at 60 psi. 2.2 gpm at 60 psi is the private lavatory limit, and 1.5 and 1.0 gpm aren't lavatory figures in the table. Metering faucets are rated by volume per cycle (0.25 gallon) rather than gpm.
Look up: IPC Table 604.4.
Source: ICC, 2021 IPC Group A code-change proposals (reproduces 2021 text)

Answer: C. 2.0 gpm at 80 psi
The 2024 IPC lowered the showerhead maximum to 2.0 gpm at 80 psi. 2.5 gpm is the 2021 figure, so if your exam still uses the 2021 edition, 2.5 is correct there. 1.8 and 1.5 gpm aren't IPC figures, although some states set lower limits by amendment. Always check the edition and amendments your exam uses.
Look up: IPC Table 604.4.
Source: ICC 2024 IPC significant changes (EduCode session) · ICC, 2021 IPC Group A code-change proposals (reproduces 2021 text)

Answer: A. At the time of installation, immediately after repairs or relocation, and at least annually
Testable assemblies must be tested when installed, after any repair or relocation, and at least once a year. A device that fails gives no visible warning, so the annual test is the only way to know it still protects the supply. Testing only once, every 5 years, or on request leaves years when a failed device goes unnoticed.
Look up: IPC 312.10.2 (2021) / 312.11.2 (2024).
Source: ICC, 2021 IPC Group A code-change proposals (reproduces 2021 text) · 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: A. Temperature not more than 210°F; pressure not more than the heater's rated working pressure or 150 psi, whichever is less
The answer is 210°F and the lesser of the rated working pressure or 150 psi. 'Whichever is greater' would let the valve stay closed above what the tank is built to handle, which is why that option is the trap. 180°F/125 psi and 250°F/200 psi aren't the code's settings.
Look up: IPC 504.5 (2024 numbering).
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: D. The top 6 inches
Hot water rises, so the hottest water sits at the top of the tank. The element must sense the top 6 inches so the valve responds to the true maximum temperature. The shallower figures aren't in the code.
Look up: IPC 504.4.1.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: C. Indirectly through an air gap
Food storage, preparation and handling equipment must discharge indirectly through an air gap, an open vertical space between the equipment's waste pipe and the receptor. That physical break means a backup can't reach the food. An air break is allowed for some other equipment, but not food storage. Direct connections, with or without a backwater valve, give sewage a path back into the equipment.
Look up: IPC 802.1.1.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: A. Indirectly through an air break
Commercial dishwashing machines discharge indirectly through an air gap or an air break. An air break (the waste pipe ends below the receptor's rim but isn't sealed into it) is allowed here, even though food storage equipment needs a full air gap. A direct trapped connection isn't allowed, and check valves and backwater valves can fail. Neither substitutes for an indirect connection.
Look up: IPC Section 802.1 (commercial dishwashing machines).
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: D. When it exceeds 30 inches in developed length measured horizontally, or 54 inches in total developed length
Past 30 inches horizontally or 54 inches in total developed length, an indirect waste pipe needs its own trap. A long pipe can foul and give off odor at its open end. The shorter figures aren't the code's numbers. Older study guides quote different limits and section numbers, so use your exam's edition.
Look up: IPC Section 802, indirect waste piping (802.3 in 2024; 802.2 in 2018).
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: A. A food waste disposer discharging into a grease interceptor
A food waste disposer must not discharge to a grease interceptor. Ground food solids fill the interceptor and stop it separating grease. Pot sinks and grease-laden prep fixtures are exactly what interceptors and automatic grease removal devices are for, so the other three installations are normal.
Look up: IPC 1003.3.1 and 1003.3.2.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: C. No; storm water must not drain into sewers intended for sewage only
Storm water is prohibited from sewers intended for sewage only, because storm surges overload sanitary sewers and treatment plants. Traps and backwater valves don't change what the sewer is designed to carry, and the code has no small-roof exception. Combined sewers are a separate case, where the local authority allows them.
Look up: IPC 1101.3.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: B. Above grade, where building occupants or maintenance personnel would normally see it
Secondary drains need their own discharge, separate from the primary system, above grade and where people will notice it. Water coming out of the secondary system is the warning that the primary drains are blocked. Tying into the primary drain or the sanitary sewer, or hiding the discharge below grade, defeats that warning.
Look up: IPC 1108.2.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: D. On the same rainfall rate as the primary system, without counting flow through the primary system
The secondary system must handle the full design storm by itself, because it exists for when the primary drains are blocked. So it's sized on the same rainfall rate, with no credit for primary flow. Half the rate undersizes it, while adding primary flow or doubling the rate oversizes it beyond what the code asks. Scuppers used as secondary drains must be at least 4 inches high.
Look up: IPC 1108.3.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org)

Answer: A. 1 per 25 for the first 50 occupants, then 1 per 50 for the remainder exceeding 50
Business occupancies use a two-step ratio: 1 water closet per 25 occupants up to 50, then 1 per 50 beyond that. The last option is the Business lavatory ratio, the usual mix-up when reading across the row. The single flat ratios aren't what the table says. When you calculate a real count, also apply 403.1.1, which covers how the total is split between sexes and how fractions are handled.
Look up: IPC Table 403.1 and 403.1.1.
Source: ICC, 2021 IPC Group A code-change proposals (reproduces 2021 text)

Answer: D. No; Business occupancies with an occupant load of 25 or fewer are exempt
Section 403.2 lists several exceptions to separate facilities, and one covers Business occupancies with a total occupant load of 25 or fewer. The general 'total occupant load of 15 or fewer' exception exists too, but this building qualifies under the Business one, so exceeding 15 doesn't matter. Drinking fountains have nothing to do with it. The 2024 edition also allows all-gender multi-user toilet rooms with stall privacy.
Look up: IPC 403.2 (exceptions).
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org) · ICC 2024 IPC significant changes (EduCode session)

Answer: B. 1 per 100 occupants
Business occupancies need 1 drinking fountain per 100 occupants, plus 1 service sink. The other ratios belong to other occupancy rows or don't appear at all. Chapter 4 also lets bottle fillers or water dispensers substitute in some cases, so check Section 410 when you size a real job.
Look up: IPC Table 403.1.
Source: ICC, 2021 IPC Group A code-change proposals (reproduces 2021 text)

Answer: C. 7.5 psig
Test pressure is at least 1½ times the proposed maximum working pressure, and never less than 3 psig. 1.5 × 5 = 7.5 psig. 3 psig is only the floor, which controls for low-pressure systems. Testing at the working pressure (5 psig) proves nothing beyond normal use. 10 psig is more than required, but it isn't the minimum.
Look up: IFGC 406.4.1.
Source: 2024 IFGC-based text (2025 Fuel Gas Code of New York State, Public.Resource.Org)

Answer: D. 1 hour
The test lasts at least ½ hour for each 500 cubic feet of pipe volume: 1,000 ÷ 500 = 2, and 2 × ½ hour = 1 hour. The 10-minute minimum applies only to systems under 10 cubic feet or to single-family dwellings, so it's the trap here. (NFPA 54, used in some states instead of the IFGC, has its own duration rules.) 30 minutes covers only 500 cubic feet.
Look up: IFGC 406.4.2.
Source: 2024 IFGC-based text (2025 Fuel Gas Code of New York State, Public.Resource.Org) · Rehoboth Beach, DE gas test form quoting 2018 IFGC 406.4.2

Source-link status — October 2, 2026: The Rehoboth Beach secondary gas-test form returned 404 and could not be independently retrieved. The primary 2024 IFGC-based New York fuel-gas source cited above remains accessible; the unavailable form is not a replacement for your jurisdiction's code.

Answer: B. 6 feet
Within 6 feet, so whoever services the appliance can shut off its gas quickly. The other distances aren't the code's figure. The section also has location and access requirements, with exceptions for some specific appliances.
Look up: IFGC 409.5.1.
Source: 2024 IFGC-based text (2025 Fuel Gas Code of New York State, Public.Resource.Org)

Answer: D. Downstream of the appliance shutoff valve, as close to the appliance inlet as practical
The sediment trap goes after the shutoff valve and close to the appliance. Debris then drops out before it reaches the controls, and the trap can be cleaned with the gas off. At the meter or upstream of the valve it can't protect the appliance as well, and sediment collects at low points, not high ones. Some appliances, such as gas ranges and clothes dryers, are exempt, but a furnace isn't.
Look up: IFGC 408.4.
Source: 2024 IFGC-based text (2025 Fuel Gas Code of New York State, Public.Resource.Org)

Answer: C. 449 gallons
Volume = 4 × 3 × 5 = 60 cubic feet, and 60 × 7.48 = 448.8, or about 449 gallons. 360 comes from multiplying 60 by 6 instead of 7.48. NIST lists 1 cubic foot as 7.481 US gallons, and exams usually round it to 7.48.
Look up: NIST Handbook 44, Appendix C (unit conversions).
Source: NIST Handbook 44 (2026), Appendix C

Answer: C. 34 inches
In a 45° offset the offset and the run are equal, so the travel is the hypotenuse: offset × √2, or offset × 1.414. 24 × 1.414 = 33.9, about 34 inches. 17 inches comes from dividing by 1.414 instead of multiplying. 24 inches assumes the travel equals the offset, and 48 inches doubles it.
Look up: Right-triangle geometry (√2 ≈ 1.414).

Answer: A. A protective system: sloping, benching, shoring or shielding
Excavations need a protective system unless they are entirely in stable rock, or less than 5 feet deep with no sign of cave-in found by a competent person. At 6 feet in soil, neither exception applies, and 'looks firm' isn't an exception. 20 feet is the depth beyond which a registered professional engineer must design the protective system, not the depth where protection starts.
Look up: 29 CFR 1926.652(a)(1).
Source: 29 CFR 1926.652 (eCFR)

Answer: B. 25 feet
No more than 25 feet of lateral travel in trenches 4 feet deep or deeper. The other distances aren't the rule. Note the different depth triggers: egress at 4 feet, protective systems at 5 feet.
Look up: 29 CFR 1926.651(c)(2).
Source: 29 CFR 1926.651 (eCFR)

Answer: B. Within three business days of the employee's first day of work
For employment lasting three business days or more, the employer completes Section 2 within three business days after the employee's first day of employment. If the job will last fewer than three business days, Section 2 is due no later than the first day; the stem excludes that exception. The employee completes Section 1 by the first day of work. State business-law sections can also test state rules, so check your bulletin.
Look up: 8 CFR 274a.2(b)(1)(ii).
Source: 8 CFR 274a.2 (eCFR)

Answer: A. At least 1½ times the regular rate for hours worked over 40 in a workweek
Federal overtime is based on the workweek, not the day, and the rate is at least time and a half for hours over 40. Daily overtime exists only under some state laws, double time isn't a federal requirement, and 44 hours is an old historical threshold. Check your state if your exam includes state business law.
Look up: 29 CFR 778.101 and 778.107.
Source: 29 CFR Part 778 (eCFR)

Answer: B. 13 DFU
Bathroom group with a 1.6-gpf water closet = 5, powder room water closet (private, 1.6 gpf) = 3, powder room lavatory = 1, domestic kitchen sink = 2, residential clothes washer = 2. Total: 5 + 3 + 1 + 2 + 2 = 13 DFU. 14 comes from adding the bathroom group's fixtures one by one (3 + 1 + 2 = 6) instead of using the bathroom-group value of 5. 11 leaves out the washer or the sink. When fixtures form a bathroom group, use the group line.
Look up: IPC Table 709.1.
Source: ICC, 2021 IPC Group A code-change proposals (reproduces 2021 text)

Answer: B. 5 inches
Fall = length × slope = 40 ft × ⅛ in/ft = 5 inches. 10 inches would be the fall at ¼ in/ft, and 20 inches at ½ in/ft. 2½ inches would be the fall at 1/16 in/ft.
Look up: Plan note 1 (length × slope).

Answer: A. 96.08 ft
The drain drops 5 inches over 40 ft (previous question). Convert to feet before subtracting: 5 ÷ 12 = 0.42 ft, so 96.50 − 0.42 = 96.08 ft. 96.00 treats 5 inches as 0.5 ft, 95.50 subtracts a full foot, and 91.50 subtracts 5 feet instead of 5 inches. Mixing inches and decimal feet is the most common error on elevation questions.
Look up: Plan notes 1 and 2 (unit conversion).

Answer: B. 3 inch
The plan's total load is 13 DFU (Question 43). Two rules apply. A building drain serving a water closet must be at least 3 inches (footnote a to Table 710.1(1)), which rules out 2 inches. A 3-inch building drain at ⅛ in/ft is rated for 36 DFU, comfortably above 13. The plan's 4-inch drain is allowed, but it isn't the minimum, and 6-inch is far larger than needed.
Look up: IPC Table 710.1(1) and footnote a.
Source: 2024 IPC-based text (2025 Plumbing Code of New York State, Public.Resource.Org) · ICC, 2021 IPC Group A code-change proposals (reproduces 2021 text)

Answer: C. No; the limit for a 1½-inch trap at ¼ inch per foot is 6 feet
Table 909.1 limits the distance from a 1½-inch trap to its vent to 6 feet at ¼ in/ft, so a 7-ft arm doesn't comply. Fix it by moving the vent closer. 8 feet is the 2-inch trap limit, 12 feet the 3-inch limit and 5 feet the 1¼-inch limit, so each wrong answer comes from reading the wrong row.
Look up: IPC Table 909.1 (2021 numbering).
Source: ICC 2021 plumbing venting brochure