NEW MEXICO JOURNEYMAN PLUMBER & GAS FITTER EXAM
COMPLETE EXAM QUESTIONS AND VERIFIED ANSWERS |
2026–2027 LATEST UPDATE | GUARANTEED PASS | DETAILED
RATIONALES | FULL STUDY GUIDE | EXAM PREP | PRACTICE
TEST | CERTIFICATION PREPARATION
SECTION ONE — QUESTIONS 1–100
1. Under the New Mexico Plumbing Code, which is based on the UPC, what is the minimum
required slope for a 3-inch horizontal drainage pipe?
A) 1/8 inch per foot
B) 1/4 inch per foot
C) 1/2 inch per foot
D) 1 inch per foot
Correct Answer: A) 1/8 inch per foot
Rationale: Under the UPC, which New Mexico adopts with state amendments, horizontal drainage
pipes 3 inches and larger must slope at least 1/8 inch per foot to maintain self-cleaning velocity. Pipes
smaller than 3 inches require 1/4 inch per foot slope. Proper slope prevents solids accumulation and
ensures adequate flow without separation .
2. What is the minimum trap seal depth required by the New Mexico Plumbing Code?
A) 1 inch
B) 2 inches
C) 3 inches
D) 4 inches
Correct Answer: B) 2 inches
Rationale: The UPC requires trap seals to be not less than 2 inches and not more than 4 inches. The 2-
inch minimum ensures an adequate water barrier against sewer gas intrusion, while the 4-inch
maximum prevents excessive water volume that could cause siphonage or trap seal loss .
3. A cleanout is required at the base of each:
A) Horizontal branch
B) Fixture drain
C) Stack
D) Vent pipe
Correct Answer: C) Stack
,Rationale: The UPC requires a cleanout at the base of each soil or waste stack to provide access for
maintenance and blockage removal. Horizontal branches require cleanouts at changes of direction,
but the stack base is a critical access point for clearing obstructions from vertical drainage systems .
4. What is the minimum residual water pressure that must be maintained at the most remote
fixture?
A) 5 psi
B) 15 psi
C) 20 psi
D) 30 psi
Correct Answer: B) 15 psi
Rationale: Plumbing systems must maintain at least 15 psi residual pressure at the most remote
fixture to ensure adequate flow and proper fixture function. This minimum pressure requirement
applies under peak demand conditions and ensures all fixtures operate as designed .
5. The maximum temperature for hot water delivered to public lavatories is generally limited to:
A) 100°F
B) 110°F
C) 120°F
D) 140°F
Correct Answer: B) 110°F
Rationale: Tempered water to public handwashing fixtures is typically limited to 110°F to prevent
scalding, especially in facilities used by children or vulnerable populations. This temperature provides
comfortable handwashing while minimizing burn risk. Commercial fixtures often include thermostatic
mixing valves to maintain this limit .
6. What is the minimum size building sewer for a single-family dwelling?
A) 2 inch
B) 3 inch
C) 4 inch
D) 6 inch
Correct Answer: C) 4 inch
Rationale: The IPC requires a minimum 4-inch building sewer for residential installations to handle
the expected waste load and provide adequate capacity for future needs. This minimum size ensures
proper drainage velocity and accommodates standard fixture unit loads for single-family dwellings .
7. A backflow preventer is required when:
, A) Water pressure exceeds 60 psi
B) A cross-connection exists
C) Pipe exceeds 100 feet
D) Water heater exceeds 50 gallons
Correct Answer: B) A cross-connection exists
Rationale: Backflow protection is required wherever a potential cross-connection exists between
potable and non-potable water systems. Backflow preventers protect the public water supply from
contamination or pollution through backsiphonage or backpressure events .
8. Under the UPC, what is the Drainage Fixture Unit (DFU) value for a standard water closet?
A) 2 DFU
B) 3 DFU
C) 4 DFU
D) 5 DFU
Correct Answer: C) 4 DFU
Rationale: Under the UPC, a standard water closet is valued at 4 DFU. New Mexico plumbers use UPC
DFU values for sizing drainage systems. This standardized rating allows accurate calculation of total
fixture unit loads to properly size building drains and sewers .
9. The minimum size building water service for a dwelling is:
A) 1/2 inch
B) 3/4 inch
C) 1 inch
D) 1-1/4 inch
Correct Answer: B) 3/4 inch
Rationale: Under the UPC, the minimum building water service is 3/4 inch for residential applications.
New Mexico follows UPC sizing requirements based on water supply fixture unit calculations,
ensuring adequate flow and pressure for all fixtures in the dwelling .
10. Which material is NOT approved for underground drainage in New Mexico?
A) Cast iron
B) PVC
C) ABS
D) Galvanized steel
Correct Answer: D) Galvanized steel
Rationale: Galvanized steel is not approved for underground drainage because it corrodes over time
when exposed to soil moisture and waste. Approved materials for underground drainage under the
UPC include cast iron, PVC, and ABS .
COMPLETE EXAM QUESTIONS AND VERIFIED ANSWERS |
2026–2027 LATEST UPDATE | GUARANTEED PASS | DETAILED
RATIONALES | FULL STUDY GUIDE | EXAM PREP | PRACTICE
TEST | CERTIFICATION PREPARATION
SECTION ONE — QUESTIONS 1–100
1. Under the New Mexico Plumbing Code, which is based on the UPC, what is the minimum
required slope for a 3-inch horizontal drainage pipe?
A) 1/8 inch per foot
B) 1/4 inch per foot
C) 1/2 inch per foot
D) 1 inch per foot
Correct Answer: A) 1/8 inch per foot
Rationale: Under the UPC, which New Mexico adopts with state amendments, horizontal drainage
pipes 3 inches and larger must slope at least 1/8 inch per foot to maintain self-cleaning velocity. Pipes
smaller than 3 inches require 1/4 inch per foot slope. Proper slope prevents solids accumulation and
ensures adequate flow without separation .
2. What is the minimum trap seal depth required by the New Mexico Plumbing Code?
A) 1 inch
B) 2 inches
C) 3 inches
D) 4 inches
Correct Answer: B) 2 inches
Rationale: The UPC requires trap seals to be not less than 2 inches and not more than 4 inches. The 2-
inch minimum ensures an adequate water barrier against sewer gas intrusion, while the 4-inch
maximum prevents excessive water volume that could cause siphonage or trap seal loss .
3. A cleanout is required at the base of each:
A) Horizontal branch
B) Fixture drain
C) Stack
D) Vent pipe
Correct Answer: C) Stack
,Rationale: The UPC requires a cleanout at the base of each soil or waste stack to provide access for
maintenance and blockage removal. Horizontal branches require cleanouts at changes of direction,
but the stack base is a critical access point for clearing obstructions from vertical drainage systems .
4. What is the minimum residual water pressure that must be maintained at the most remote
fixture?
A) 5 psi
B) 15 psi
C) 20 psi
D) 30 psi
Correct Answer: B) 15 psi
Rationale: Plumbing systems must maintain at least 15 psi residual pressure at the most remote
fixture to ensure adequate flow and proper fixture function. This minimum pressure requirement
applies under peak demand conditions and ensures all fixtures operate as designed .
5. The maximum temperature for hot water delivered to public lavatories is generally limited to:
A) 100°F
B) 110°F
C) 120°F
D) 140°F
Correct Answer: B) 110°F
Rationale: Tempered water to public handwashing fixtures is typically limited to 110°F to prevent
scalding, especially in facilities used by children or vulnerable populations. This temperature provides
comfortable handwashing while minimizing burn risk. Commercial fixtures often include thermostatic
mixing valves to maintain this limit .
6. What is the minimum size building sewer for a single-family dwelling?
A) 2 inch
B) 3 inch
C) 4 inch
D) 6 inch
Correct Answer: C) 4 inch
Rationale: The IPC requires a minimum 4-inch building sewer for residential installations to handle
the expected waste load and provide adequate capacity for future needs. This minimum size ensures
proper drainage velocity and accommodates standard fixture unit loads for single-family dwellings .
7. A backflow preventer is required when:
, A) Water pressure exceeds 60 psi
B) A cross-connection exists
C) Pipe exceeds 100 feet
D) Water heater exceeds 50 gallons
Correct Answer: B) A cross-connection exists
Rationale: Backflow protection is required wherever a potential cross-connection exists between
potable and non-potable water systems. Backflow preventers protect the public water supply from
contamination or pollution through backsiphonage or backpressure events .
8. Under the UPC, what is the Drainage Fixture Unit (DFU) value for a standard water closet?
A) 2 DFU
B) 3 DFU
C) 4 DFU
D) 5 DFU
Correct Answer: C) 4 DFU
Rationale: Under the UPC, a standard water closet is valued at 4 DFU. New Mexico plumbers use UPC
DFU values for sizing drainage systems. This standardized rating allows accurate calculation of total
fixture unit loads to properly size building drains and sewers .
9. The minimum size building water service for a dwelling is:
A) 1/2 inch
B) 3/4 inch
C) 1 inch
D) 1-1/4 inch
Correct Answer: B) 3/4 inch
Rationale: Under the UPC, the minimum building water service is 3/4 inch for residential applications.
New Mexico follows UPC sizing requirements based on water supply fixture unit calculations,
ensuring adequate flow and pressure for all fixtures in the dwelling .
10. Which material is NOT approved for underground drainage in New Mexico?
A) Cast iron
B) PVC
C) ABS
D) Galvanized steel
Correct Answer: D) Galvanized steel
Rationale: Galvanized steel is not approved for underground drainage because it corrodes over time
when exposed to soil moisture and waste. Approved materials for underground drainage under the
UPC include cast iron, PVC, and ABS .
