10 exam-style questions with answers and explanations, straight from our 1,030-question bank. Tap an answer to check yourself. When you're ready, take the scored version in the free practice test.
The NJ-MP exam has 100 questions and runs 3 hours 15 minutes.
These 10 free NJ-MP questions are organized by exam domain, so you can see how each part of the New Jersey Master Plumber License Exam blueprint is tested. Reveal the answer and explanation under each question.
A proposed CPVC hot-water line will operate at 85 psi and 180 °F. The pipe is rated for 160 psi at 73 °F and 100 psi at 180 °F. A union in the line is rated for 150 psi at 73 °F but only 80 psi at 180 °F. Joint compatibility and water-service approvals are satisfactory. Which disposition of the submittal is justified?
Correct answer: C - Replace only the union with a compatible one rated for 100 psi at 180 °F.
A chemically treated boiler loop presents a health-hazard cross-connection at its potable-water makeup line. The loop pump can raise pressure at that connection above the potable supply pressure. The water supplier permits an approved mechanical backflow assembly, and its installation clearances and relief drainage can be provided. Which device protects against the stated hazard and pressure reversal?
Correct answer: A - A reduced-pressure-principle backflow assembly
Sewer odor returns at a seldom-used floor drain after several idle weeks. Refilling the trap stops the odor. The trap then holds water overnight, and nearby fixture discharges cause neither gurgling nor a visible change in its seal. Which repair proposal targets the pattern actually observed?
Correct answer: D - Install approved trap-seal replenishment for periods of nonuse.
A home's water heater began discharging briefly through its temperature-and-pressure relief valve after a check valve was installed at the water service. Discharge occurs only during reheating with all fixtures closed. Supply pressure is normal between heating cycles, and the thermostat and relief valve test correctly. There is no expansion-control device. Which modification addresses the cause?
Correct answer: B - Add a sized potable-water expansion tank downstream of the check valve.
A building has weak water flow. Calibrated gauges immediately before and after its service strainer are at the same elevation. Both read 68 psi with no flow. During a 7-gpm draw, the upstream gauge reads 66 psi and the downstream gauge reads 34 psi; the strainer's specified clean pressure drop at that flow is no more than 3 psi. What work should be authorized first?
Correct answer: B - Isolate, depressurize, and service the strainer; repeat the flow test.
During construction work inside a permit-required sewage vault, an entrant collapses. The attendant remains outside, and the oxygen monitor alarms at 18.3 percent. No non-entry retrieval is feasible. A nearby coworker who is not trained or equipped for entry rescue approaches the hatch to help. What is the attendant's immediate responsibility?
Correct answer: A - Block additional entry and immediately summon the designated rescue service.
During a large fixture discharge, air bubbles outward through a full floor-drain trap. A manometer confirms positive pressure on the drainage side of the seal. An installer recommends replacing the nearby air-admittance valve with a larger model. Which response is technically justified?
Correct answer: A - Investigate downstream restrictions and the open vent path; an air-admittance valve cannot relieve positive pressure.
Two horizontal pipe runs are parallel and point north. The second run is 8 inches east and 15 inches above the first. A rolling offset will connect them using two 45-degree elbows. Each elbow's center-to-pipe-end takeout is 1.25 inches. What straight-pipe cut length is needed between the elbows, to the nearest hundredth of an inch?
Correct answer: B - 21.54 inches
An engineer's response to a request for information changes a pipe route and adds labor. The contract reserves approval of price and time changes to the owner's named representative and requires unaffected work to continue. There is no emergency. The foreman asks whether the crew should start the reroute. How should the master plumber handle the instruction?
Correct answer: D - Hold the reroute for authorized change approval; continue unaffected work.
A contractor bids an exempt capital improvement for a private, nonexempt New Jersey property owner who supplies a valid Form ST-8. Ordinary plumbing materials to be incorporated into the property cost $8,000 before sales tax; loaded labor costs $3,470. These are the only job costs. The New Jersey sales-tax rate is 6.625 percent. Which lump-sum price produces a 20 percent gross margin on the selling price?
Correct answer: D - $15,000.00
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