New Mexico MM-98 Mechanical Contractor Exam
100 Complete Questions And Answers | Content
Well Organized 2026/2027 Newest Update | 100 %
Rated And Verified Solutions | Get An A+ New
Version!!! Instant Pdf
1. In a DWV system, what is the primary function of a vent pipe?
A. Remove solids
B. Increase flow velocity
C. Equalize pressure in the system
D. Heat wastewater
Answer: C
Explanation: Venting prevents pressure fluctuations that could siphon traps
and allow sewer gases to enter the building.
2. What is the minimum slope for a 3-inch horizontal drainage pipe?
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
Answer: B
Explanation: Plumbing codes typically require 1/8 inch per foot for pipes 3
inches or larger.
3. Which device prevents backflow in a potable water system?
A. Expansion tank
B. Check valve
C. Backflow preventer
D. Pressure regulator
Answer: C
, Explanation: A backflow preventer stops contaminated water from reversing
into clean water supply.
4. What is the purpose of a P-trap?
A. Increase flow
B. Prevent sewer gas entry
C. Filter debris
D. Improve pressure
Answer: B
Explanation: The trap holds water to block sewer gases.
5. Which refrigerant classification is considered non-toxic and non-flammable?
A. A1
B. B2
C. A3
D. B1
Answer: A
Explanation: A1 refrigerants have low toxicity and no flame propagation.
6. What is superheat in HVAC systems?
A. Heat above boiling point
B. Heat removed from liquid
C. Temperature above saturation temperature
D. Pressure increase
Answer: C
Explanation: Superheat measures vapor temperature above its saturation
point.
7. Which component controls gas flow in a furnace burner?
A. Thermostat
B. Gas valve
C. Heat exchanger
D. Blower motor
Answer: B
Explanation: The gas valve regulates fuel supply.
, 8. What is the main purpose of insulation on refrigerant lines?
A. Prevent corrosion
B. Improve aesthetics
C. Reduce heat gain/loss
D. Increase pressure
Answer: C
Explanation: Insulation maintains system efficiency.
9. What is the minimum clearance for a gas water heater from combustibles
(typical)?
A. 1 inch
B. 6 inches
C. 12 inches
D. 24 inches
Answer: B
Explanation: Standard codes require at least 6 inches clearance.
10.Which gas is commonly used for leak testing piping systems?
A. Oxygen
B. Nitrogen
C. Hydrogen
D. Carbon monoxide
Answer: B
Explanation: Nitrogen is inert and safe for pressure testing.
11.What does BTU measure?
A. Pressure
B. Heat energy
C. Flow rate
D. Velocity
Answer: B
Explanation: BTU quantifies heat energy.
12.Which tool is used to measure refrigerant pressure?
A. Thermometer
100 Complete Questions And Answers | Content
Well Organized 2026/2027 Newest Update | 100 %
Rated And Verified Solutions | Get An A+ New
Version!!! Instant Pdf
1. In a DWV system, what is the primary function of a vent pipe?
A. Remove solids
B. Increase flow velocity
C. Equalize pressure in the system
D. Heat wastewater
Answer: C
Explanation: Venting prevents pressure fluctuations that could siphon traps
and allow sewer gases to enter the building.
2. What is the minimum slope for a 3-inch horizontal drainage pipe?
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
Answer: B
Explanation: Plumbing codes typically require 1/8 inch per foot for pipes 3
inches or larger.
3. Which device prevents backflow in a potable water system?
A. Expansion tank
B. Check valve
C. Backflow preventer
D. Pressure regulator
Answer: C
, Explanation: A backflow preventer stops contaminated water from reversing
into clean water supply.
4. What is the purpose of a P-trap?
A. Increase flow
B. Prevent sewer gas entry
C. Filter debris
D. Improve pressure
Answer: B
Explanation: The trap holds water to block sewer gases.
5. Which refrigerant classification is considered non-toxic and non-flammable?
A. A1
B. B2
C. A3
D. B1
Answer: A
Explanation: A1 refrigerants have low toxicity and no flame propagation.
6. What is superheat in HVAC systems?
A. Heat above boiling point
B. Heat removed from liquid
C. Temperature above saturation temperature
D. Pressure increase
Answer: C
Explanation: Superheat measures vapor temperature above its saturation
point.
7. Which component controls gas flow in a furnace burner?
A. Thermostat
B. Gas valve
C. Heat exchanger
D. Blower motor
Answer: B
Explanation: The gas valve regulates fuel supply.
, 8. What is the main purpose of insulation on refrigerant lines?
A. Prevent corrosion
B. Improve aesthetics
C. Reduce heat gain/loss
D. Increase pressure
Answer: C
Explanation: Insulation maintains system efficiency.
9. What is the minimum clearance for a gas water heater from combustibles
(typical)?
A. 1 inch
B. 6 inches
C. 12 inches
D. 24 inches
Answer: B
Explanation: Standard codes require at least 6 inches clearance.
10.Which gas is commonly used for leak testing piping systems?
A. Oxygen
B. Nitrogen
C. Hydrogen
D. Carbon monoxide
Answer: B
Explanation: Nitrogen is inert and safe for pressure testing.
11.What does BTU measure?
A. Pressure
B. Heat energy
C. Flow rate
D. Velocity
Answer: B
Explanation: BTU quantifies heat energy.
12.Which tool is used to measure refrigerant pressure?
A. Thermometer
