CO Mechanical Contractor Exam
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. Which of the following is the primary purpose of a mechanical
contractor?
A. Design electrical systems
B. Install plumbing, HVAC, and mechanical systems
C. Perform roofing work
D. Manage landscaping
B. Install plumbing, HVAC, and mechanical systems
Rationale: Mechanical contractors specialize in the installation,
maintenance, and repair of mechanical systems, including plumbing,
HVAC, and refrigeration.
2. What is the typical minimum PSI for domestic water supply piping?
A. 20 PSI
B. 30 PSI
C. 40 PSI
D. 50 PSI
B. 30 PSI
Rationale: Domestic water systems are generally designed to maintain a
minimum pressure of 30 PSI to ensure adequate flow at fixtures.
3. Which type of piping is most commonly used for high-pressure steam
systems?
A. PVC
B. CPVC
, C. Black steel
D. PEX
C. Black steel
Rationale: Black steel piping is suitable for high-temperature and high-
pressure steam applications.
4. What is the standard maximum allowable slope for horizontal drainage
piping?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
B. 1/4 inch per foot
Rationale: Horizontal drainage piping must slope at least 1/4 inch per foot
to ensure proper flow and prevent clogging.
5. Which device is used to prevent backflow in a potable water system?
A. Pressure relief valve
B. Check valve
C. Gate valve
D. Butterfly valve
B. Check valve
Rationale: Check valves allow water to flow in one direction only,
preventing contamination from backflow.
6. What is the main purpose of a pressure-reducing valve in a mechanical
system?
A. Increase system pressure
B. Reduce excessive inlet pressure to a safe level
C. Control water temperature
D. Filter water
B. Reduce excessive inlet pressure to a safe level
Rationale: Pressure-reducing valves protect piping and fixtures by
maintaining safe operating pressure.
, 7. In HVAC systems, what does BTU stand for?
A. British Thermal Unit
B. Boiler Temperature Unit
C. Basic Thermal Usage
D. Bulk Transfer Unit
A. British Thermal Unit
Rationale: BTU measures the amount of heat energy required to raise the
temperature of one pound of water by one degree Fahrenheit.
8. What type of HVAC system uses a central air handler and ductwork to
distribute conditioned air?
A. Packaged terminal unit
B. Split system
C. Central air system
D. Evaporative cooler
C. Central air system
Rationale: Central air systems use a single air handler connected to
ductwork to provide conditioned air throughout a building.
9. Which mechanical code sets the minimum standards for plumbing
systems in the U.S.?
A. NEC
B. UPC
C. NFPA
D. IBC
B. UPC
Rationale: The Uniform Plumbing Code (UPC) establishes standards for
the design, installation, and maintenance of plumbing systems.
10. What is the main function of a heat exchanger in mechanical
systems?
A. Store water
B. Transfer heat between two fluids
C. Filter impurities
D. Increase system pressure
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. Which of the following is the primary purpose of a mechanical
contractor?
A. Design electrical systems
B. Install plumbing, HVAC, and mechanical systems
C. Perform roofing work
D. Manage landscaping
B. Install plumbing, HVAC, and mechanical systems
Rationale: Mechanical contractors specialize in the installation,
maintenance, and repair of mechanical systems, including plumbing,
HVAC, and refrigeration.
2. What is the typical minimum PSI for domestic water supply piping?
A. 20 PSI
B. 30 PSI
C. 40 PSI
D. 50 PSI
B. 30 PSI
Rationale: Domestic water systems are generally designed to maintain a
minimum pressure of 30 PSI to ensure adequate flow at fixtures.
3. Which type of piping is most commonly used for high-pressure steam
systems?
A. PVC
B. CPVC
, C. Black steel
D. PEX
C. Black steel
Rationale: Black steel piping is suitable for high-temperature and high-
pressure steam applications.
4. What is the standard maximum allowable slope for horizontal drainage
piping?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
B. 1/4 inch per foot
Rationale: Horizontal drainage piping must slope at least 1/4 inch per foot
to ensure proper flow and prevent clogging.
5. Which device is used to prevent backflow in a potable water system?
A. Pressure relief valve
B. Check valve
C. Gate valve
D. Butterfly valve
B. Check valve
Rationale: Check valves allow water to flow in one direction only,
preventing contamination from backflow.
6. What is the main purpose of a pressure-reducing valve in a mechanical
system?
A. Increase system pressure
B. Reduce excessive inlet pressure to a safe level
C. Control water temperature
D. Filter water
B. Reduce excessive inlet pressure to a safe level
Rationale: Pressure-reducing valves protect piping and fixtures by
maintaining safe operating pressure.
, 7. In HVAC systems, what does BTU stand for?
A. British Thermal Unit
B. Boiler Temperature Unit
C. Basic Thermal Usage
D. Bulk Transfer Unit
A. British Thermal Unit
Rationale: BTU measures the amount of heat energy required to raise the
temperature of one pound of water by one degree Fahrenheit.
8. What type of HVAC system uses a central air handler and ductwork to
distribute conditioned air?
A. Packaged terminal unit
B. Split system
C. Central air system
D. Evaporative cooler
C. Central air system
Rationale: Central air systems use a single air handler connected to
ductwork to provide conditioned air throughout a building.
9. Which mechanical code sets the minimum standards for plumbing
systems in the U.S.?
A. NEC
B. UPC
C. NFPA
D. IBC
B. UPC
Rationale: The Uniform Plumbing Code (UPC) establishes standards for
the design, installation, and maintenance of plumbing systems.
10. What is the main function of a heat exchanger in mechanical
systems?
A. Store water
B. Transfer heat between two fluids
C. Filter impurities
D. Increase system pressure
