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Exam Review

Key Facts: NM Plumbing Inspector Exam

75%

Passing Score

PSI NM Contractor Bulletin 4/3/2026

75 Q

Official Exam Questions

PSI NM Contractor Bulletin 4/3/2026

200 min

Time Allowed

PSI NM Contractor Bulletin 4/3/2026

USD 68.88

PSI Exam Fee

PSI NM Contractor Bulletin 4/3/2026

NM CID Plumbing Inspector is a 75-question PSI exam, 75% pass, 200 minutes, USD 68.88, open-book UPC/NMAC plumbing and liquid-waste rules (bulletin 4/3/2026).

Sample NM Plumbing Inspector Practice Questions

Try these sample questions to review concepts for the NM Plumbing Inspector exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1An inspector checking a private bathtub or combination bath/shower on a New Mexico CID plan review assigns how many drainage fixture units (DFU) from UPC 2021 Table 702.1?
A.1 DFU
B.2 DFU
C.3 DFU
D.4 DFU
Explanation: UPC 2021 Table 702.1 assigns 2 DFU to a bathtub or combination bath/shower and requires a 1-1/2 inch trap and trap arm. Inspectors use that table, not water-supply fixture units, when checking drainage load. A 1 DFU value belongs to a private lavatory or bidet, and 3 DFU belongs to a domestic clothes-washer standpipe.
2During drainage sizing review, what DFU value does UPC 2021 Table 702.1 assign to a private 1.6 GPF gravity-tank water closet?
A.2 DFU
B.3 DFU
C.4 DFU
D.6 DFU
Explanation: Table 702.1 rates a 1.6 GPF gravity-tank water closet at 3 DFU. A 1.6 GPF flushometer-valve water closet is 4 DFU, and a greater-than-1.6 GPF flushometer-valve water closet is 6 DFU. Inspectors must read the flush type, not just “water closet,” before accepting a stack or branch size.
3A residential clothes-washer standpipe is submitted for inspection. Per UPC 2021 Table 702.1, what are the minimum trap/trap-arm size and the DFU value?
A.1-1/2 inch trap and 2 DFU
B.2 inch trap and 2 DFU
C.2 inch trap and 3 DFU
D.3 inch trap and 4 DFU
Explanation: Table 702.1 lists a domestic clothes-washer standpipe as a 2 inch trap and trap arm with 3 DFU. A 1-1/2 inch trap is the bathtub listing, and a 2 DFU assignment belongs to a shower or dishwasher, not the washer standpipe. Inspectors should also confirm the standpipe height in Chapter 8 before approving the rough-in.
4What minimum trap and trap-arm size and DFU value does UPC 2021 Table 702.1 assign to a single-head shower?
A.1-1/2 inch and 2 DFU
B.2 inch and 2 DFU
C.2 inch and 3 DFU
D.1-1/4 inch and 1 DFU
Explanation: A single-head shower is listed at 2 DFU with a 2 inch trap and trap arm. Note 9 allows a 1-1/2 inch trap only for a limited bathtub-to-shower retrofit, not for a new shower. Each additional shower head adds 1 DFU on the same 2 inch trap listing.
5Unless a UPC 2021 Section 708.1 exception is first approved by the authority having jurisdiction, what is the minimum uniform slope of horizontal drainage piping?
A.1/16 inch per foot
B.1/8 inch per foot
C.1/4 inch per foot
D.1/2 inch per foot
Explanation: UPC 708.1 requires horizontal drainage piping to run in practical alignment at a uniform slope of not less than 1/4 inch per foot (2 percent) toward the point of disposal. A flatter 1/8 inch per foot slope is allowed only on 4 inch and larger pipe when 1/4 inch per foot is impractical and the AHJ first approves it. Inspectors should reject an unapproved 1/8 inch slope on 2 inch or 3 inch waste.
6A contractor asks to flatten a 4 inch building drain to 1/8 inch per foot because the street sewer is shallow. Under UPC 2021 Section 708.1, when may the inspector accept that slope?
A.Anytime the pipe is 3 inches or larger
B.Only if the pipe is 4 inches or larger, 1/4 inch per foot is impractical, and the AHJ first approves it
C.Never; 1/4 inch per foot is mandatory on every drain
D.Only if the drain is plastic
Explanation: Section 708.1 allows 4 inch and larger piping to slope not less than 1/8 inch per foot where 1/4 inch per foot is impractical because of street-sewer depth, structure, or building arrangement, and only after AHJ approval. Three-inch pipe stays at 1/4 inch per foot. Material type does not create the exception.
7Per UPC 2021 Table 703.2, what is the maximum drainage fixture-unit load on a 2 inch horizontal drain (excluding the trap-arm column and water closets)?
A.4 DFU
B.6 DFU
C.8 DFU
D.16 DFU
Explanation: Table 703.2 allows 8 DFU on a 2 inch horizontal drain and 16 DFU on a 2 inch vertical drain. Note 3 excludes six-unit traps and water closets from 2 inch piping. Six DFU is an IPC horizontal-branch figure and is not the UPC 2 inch horizontal listing New Mexico inspectors use.
8A 3 inch horizontal waste branch is proposed to carry 32 DFU with no water closets. Using UPC 2021 Table 703.2, what should the inspector conclude?
A.Reject it; a 3 inch horizontal drain is limited to 20 DFU
B.Accept it; a 3 inch horizontal drain is limited to 35 DFU
C.Reject it; a 3 inch horizontal drain is limited to 16 DFU
D.Accept it only if the slope is 1/8 inch per foot
Explanation: Table 703.2 lists 35 DFU on a 3 inch horizontal drain (note 4 limits water closets, which this branch does not have). Thirty-two DFU is within 35, so the size is acceptable at the standard 1/4 inch per foot slope. Twenty DFU is not the UPC 3 inch horizontal number.
9An inspector measures a 1-1/2 inch lavatory trap arm sloped at 1/4 inch per foot. Per UPC 2021 Table 1002.2, what is the maximum developed length from the trap weir to the inner edge of the vent?
A.30 inches
B.42 inches
C.60 inches
D.72 inches
Explanation: Table 1002.2 allows a 1-1/2 inch trap arm a maximum of 42 inches, with a minimum trap-to-vent distance of 3 inches (and never less than two pipe diameters). Thirty inches is the 1-1/4 inch maximum, 60 inches is the 2 inch maximum, and 72 inches is the 3 inch maximum.
10Per UPC 2021 Table 1002.2 Note 2, what is the maximum developed length from the top of a water-closet flange to the inner edge of its vent?
A.42 inches
B.5 feet
C.6 feet
D.10 feet
Explanation: Note 2 to Table 1002.2 states that the developed length between a water closet or similar fixture trap, measured from the top of the closet flange to the inner edge of the vent, shall not exceed 6 feet. The inch-based columns in the table do not apply to water closets. Inspectors should reject a 10 foot water-closet trap arm.

About the NM Plumbing Inspector Exam

The New Mexico CID Plumbing Inspector Examination is the open-book PSI inspector exam covering the New Mexico Plumbing Code (NMAC 14.8.2, 2015), Uniform Plumbing Code 2021, NFPA 54 (2015), New Mexico Liquid Waste Disposal Regulations (NMAC 20.7.3, 2005), New Mexico Mechanical Code (NMAC 14.9.2, 2015), and Uniform Mechanical Code 2021. The official exam has 75 scored questions, a 75% passing standard (57 points), and 200 minutes allowed. PSI lists the fee at USD 68.88 (bulletin updated 4/3/2026). This English-language MCQ bank is a study aid, not an official PSI form.

Exam sponsor: PSI Services LLC (for New Mexico Construction Industries Division). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Questions

75 questions

Time Limit

200 minutes

Passing Score

75% (57 of 75 points)

Exam / Certification Fees

USD 68.88

Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

27%

Drainage Waste and Vents

DWV design, sizing, and inspection (20 items)

13%

Water Supply Systems

Potable water supply and distribution (10 items)

11%

Backflow Prevention

Backflow assemblies and protection (8 items)

7%

Storm Drainage Systems

Storm drainage inspection (5 items)

12%

Plumbing Fixtures, Including Water Heaters

Fixtures and water heaters (9 items)

16%

General Regulations

Administration and general plumbing regulations (12 items)

8%

Interceptors and Traps

Interceptors, separators, and traps (6 items)

7%

Septic and Sewer

Septic systems and building sewers (5 items)

Preparing for the NM Plumbing Inspector Exam

What You Need to Know

  • Passing score: 75% (57 of 75 points)
  • Exam length: 75 questions
  • Time limit: 200 minutes
  • Exam / certification fees: USD 68.88 Official sources

Using Our Practice Resources

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

NM Plumbing Inspector: Suggested Study Strategy

1Drill DFU, vent, trap-arm, and water-supply fixture-unit sizing from UPC 2021
2Review NMAC 20.7.3 liquid-waste rules for septic items
3This bank is an English-language MCQ study aid, not an official PSI inspector form

Frequently Asked Questions

How many questions are on the NM Plumbing Inspector exam?

The official PSI examination has 75 scored questions. Passing is 75% (57 points) within 200 minutes (bulletin updated 4/3/2026).

What references are allowed?

NMAC 14.8.2 (2015), UPC 2021, NFPA 54 (2015), NMAC 20.7.3 (2005), NMAC 14.9.2 (2015), and UMC 2021.