CO Master Plumber Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. A Colorado Master Plumber is supervising a plumbing installation in
a commercial building where the water service enters the structure
and supplies multiple fixtures. Which principle is most important
when determining the required size of the building water supply
piping?
A. The pipe must always match the size of the municipal water main
B. The pipe size is based solely on the number of bathrooms
C. The pipe size must be determined using the applicable demand,
available pressure, developed length, elevation, and sizing method
required by code
D. The pipe must be at least one nominal size larger than the building
sewer
The required water-service size depends on hydraulic demand and
system conditions, including fixture demand, pressure, length, and
elevation. Simply matching the municipal main or counting bathrooms is
insufficient.
, 2. A plumbing contractor is installing a potable-water distribution
system in a building. Which condition would create the greatest
concern for protecting the potable water supply?
A. Installing a shutoff valve on each branch
B. Using larger-than-required distribution piping
C. Allowing a potential cross-connection between potable water and a
contaminated source
D. Installing insulation around hot-water piping
A cross-connection can allow contaminated water to enter the potable
system through backflow. Backflow prevention and proper separation
are therefore fundamental requirements of potable-water protection.
3. A fixture is connected to a drainage system through a trap. What is
the primary purpose of the trap?
A. To increase drainage velocity
B. To prevent water hammer
C. To maintain a water seal that prevents sewer gases from entering the
occupied space
D. To increase the available water pressure
A properly designed trap retains a water seal that separates the
drainage system from the occupied space and helps prevent the passage
of sewer gases.
, 4. A Master Plumber is evaluating a drainage system that repeatedly
loses trap seals because of pressure fluctuations within the drainage
piping. Which plumbing principle should be investigated first?
A. Excessive water pressure
B. Improper venting or excessive trap siphonage
C. Oversized water-service piping
D. Insufficient thermal expansion
Drainage-system pressure changes can siphon or blow trap seals away
when the vent system is improperly designed. Proper venting maintains
atmospheric pressure and protects trap seals.
5. In a typical sanitary drainage system, what is the primary function of
a vent system?
A. To carry sewage to the public sewer
B. To supply potable water to fixtures
C. To protect trap seals and allow proper circulation of air within the
drainage system
D. To increase the pressure of discharge piping
Drainage vents allow air movement within the drainage system and
help prevent pressure conditions that could destroy trap seals or
interfere with drainage flow.
6. A plumbing installer is determining the drainage load imposed by
several plumbing fixtures. Which unit is generally used to express
the relative drainage load of fixtures?
, A. PSI
B. GPM
C. Drainage fixture units
D. BTU/h
Drainage fixture units provide a standardized method of expressing the
relative load that plumbing fixtures impose on a drainage system for
sizing purposes.
7. When sizing a sanitary drainage pipe, which factor is particularly
important in addition to the total drainage fixture-unit load?
A. Paint color of the pipe
B. Fixture manufacturer’s logo
C. The allowable pipe slope and resulting carrying capacity
D. The temperature of the building's drinking water
Drainage piping must be sized and installed with an appropriate slope
so that the pipe can transport the expected discharge while maintaining
effective self-scouring flow.
8. A building sewer is installed with insufficient slope. What is the
most likely consequence?
A. Excessive water pressure
B. Increased hot-water temperature
C. Reduced drainage velocity and increased potential for solids to settle
in the piping
D. Increased potable-water pressure
Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. A Colorado Master Plumber is supervising a plumbing installation in
a commercial building where the water service enters the structure
and supplies multiple fixtures. Which principle is most important
when determining the required size of the building water supply
piping?
A. The pipe must always match the size of the municipal water main
B. The pipe size is based solely on the number of bathrooms
C. The pipe size must be determined using the applicable demand,
available pressure, developed length, elevation, and sizing method
required by code
D. The pipe must be at least one nominal size larger than the building
sewer
The required water-service size depends on hydraulic demand and
system conditions, including fixture demand, pressure, length, and
elevation. Simply matching the municipal main or counting bathrooms is
insufficient.
, 2. A plumbing contractor is installing a potable-water distribution
system in a building. Which condition would create the greatest
concern for protecting the potable water supply?
A. Installing a shutoff valve on each branch
B. Using larger-than-required distribution piping
C. Allowing a potential cross-connection between potable water and a
contaminated source
D. Installing insulation around hot-water piping
A cross-connection can allow contaminated water to enter the potable
system through backflow. Backflow prevention and proper separation
are therefore fundamental requirements of potable-water protection.
3. A fixture is connected to a drainage system through a trap. What is
the primary purpose of the trap?
A. To increase drainage velocity
B. To prevent water hammer
C. To maintain a water seal that prevents sewer gases from entering the
occupied space
D. To increase the available water pressure
A properly designed trap retains a water seal that separates the
drainage system from the occupied space and helps prevent the passage
of sewer gases.
, 4. A Master Plumber is evaluating a drainage system that repeatedly
loses trap seals because of pressure fluctuations within the drainage
piping. Which plumbing principle should be investigated first?
A. Excessive water pressure
B. Improper venting or excessive trap siphonage
C. Oversized water-service piping
D. Insufficient thermal expansion
Drainage-system pressure changes can siphon or blow trap seals away
when the vent system is improperly designed. Proper venting maintains
atmospheric pressure and protects trap seals.
5. In a typical sanitary drainage system, what is the primary function of
a vent system?
A. To carry sewage to the public sewer
B. To supply potable water to fixtures
C. To protect trap seals and allow proper circulation of air within the
drainage system
D. To increase the pressure of discharge piping
Drainage vents allow air movement within the drainage system and
help prevent pressure conditions that could destroy trap seals or
interfere with drainage flow.
6. A plumbing installer is determining the drainage load imposed by
several plumbing fixtures. Which unit is generally used to express
the relative drainage load of fixtures?
, A. PSI
B. GPM
C. Drainage fixture units
D. BTU/h
Drainage fixture units provide a standardized method of expressing the
relative load that plumbing fixtures impose on a drainage system for
sizing purposes.
7. When sizing a sanitary drainage pipe, which factor is particularly
important in addition to the total drainage fixture-unit load?
A. Paint color of the pipe
B. Fixture manufacturer’s logo
C. The allowable pipe slope and resulting carrying capacity
D. The temperature of the building's drinking water
Drainage piping must be sized and installed with an appropriate slope
so that the pipe can transport the expected discharge while maintaining
effective self-scouring flow.
8. A building sewer is installed with insufficient slope. What is the
most likely consequence?
A. Excessive water pressure
B. Increased hot-water temperature
C. Reduced drainage velocity and increased potential for solids to settle
in the piping
D. Increased potable-water pressure
