Michigan Plumbing Contractor Exams
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. In Michigan, a plumbing permit is required before beginning any work
except:
A. Installation of a new water heater
B. Minor repairs that do not involve alteration of fixtures, pipes, or
appliances
C. Replacement of a sink
D. Installation of a sewer line
Rationale: Minor repairs that do not alter plumbing systems are
exempt from permit requirements under Michigan plumbing law.
2. The primary purpose of a vent in a plumbing system is to:
A. Increase water pressure
B. Prevent corrosion
C. Allow air into the drainage system to prevent trap siphoning
D. Heat waste water
Rationale: Vents equalize pressure in drain lines and prevent traps
from being siphoned, maintaining proper function.
3. An S-trap is no longer permitted because it:
A. Uses too much water
B. Is expensive to install
C. Is prone to siphoning and loss of trap seal
D. Requires larger pipes
, Rationale: S-traps readily siphon, allowing sewer gases into
buildings, so modern codes prohibit them.
4. The minimum slope for a 3-inch horizontal drain line is:
A. 1/8 inch per foot
B. 1/2 inch per foot
C. 1/4 inch per foot
D. 3/4 inch per foot
Rationale: Code mandates a minimum of 1/4 inch per foot slope for
3-inch drains for proper gravity flow.
5. Backflow prevention is required when:
A. Installing new faucets
B. Testing water pressure
C. Cleaning drains
D. There is a cross-connection with a potential contamination source
Rationale: Backflow devices are mandated wherever backflow risk
exists to protect potable water from contamination.
6. In Michigan code, a building sewer must be at least how many
feet from a private well?
A. 5 feet
B. 10 feet
C. 50 feet
D. 100 feet
Rationale: Michigan plumbing rules require a minimum 50-foot
horizontal separation between sewers and water supply wells.
7. A cleanout is required at a maximum of how many feet in a
straight run of horizontal drainage piping?
A. 50 feet
B. 100 feet
C. 75 feet
D. 150 feet
, Rationale: To allow maintenance, cleanouts are required at
maximum intervals specified by code, often 75 feet.
8. Indirect waste connections are required to be trapped to
prevent:
A. Corrosion
B. Slow drains
C. Sewer gas entry
D. High pH
Rationale: Traps on indirect wastes prevent sewer gas from entering
the building.
9. Fixture units are used for:
A. Water heating calculations
B. Electrical load sizing
C. Sizing of drainage and vent systems
D. Estimating material cost
Rationale: Drainage Fixture Units help determine correct pipe sizes
and capacities.
10. The required potable water supply pressure in Michigan typically
must be at least:
A. 10 psi
B. 20 psi
C. 30 psi
D. 60 psi
Rationale: A minimum 30 psi is generally required at fixtures for
adequate performance.
11. A water service line cannot be smaller than:
A. 3/4 inch
B. 1/4 inch
C. 3/4 inch for single-family residential
D. 2 inches
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. In Michigan, a plumbing permit is required before beginning any work
except:
A. Installation of a new water heater
B. Minor repairs that do not involve alteration of fixtures, pipes, or
appliances
C. Replacement of a sink
D. Installation of a sewer line
Rationale: Minor repairs that do not alter plumbing systems are
exempt from permit requirements under Michigan plumbing law.
2. The primary purpose of a vent in a plumbing system is to:
A. Increase water pressure
B. Prevent corrosion
C. Allow air into the drainage system to prevent trap siphoning
D. Heat waste water
Rationale: Vents equalize pressure in drain lines and prevent traps
from being siphoned, maintaining proper function.
3. An S-trap is no longer permitted because it:
A. Uses too much water
B. Is expensive to install
C. Is prone to siphoning and loss of trap seal
D. Requires larger pipes
, Rationale: S-traps readily siphon, allowing sewer gases into
buildings, so modern codes prohibit them.
4. The minimum slope for a 3-inch horizontal drain line is:
A. 1/8 inch per foot
B. 1/2 inch per foot
C. 1/4 inch per foot
D. 3/4 inch per foot
Rationale: Code mandates a minimum of 1/4 inch per foot slope for
3-inch drains for proper gravity flow.
5. Backflow prevention is required when:
A. Installing new faucets
B. Testing water pressure
C. Cleaning drains
D. There is a cross-connection with a potential contamination source
Rationale: Backflow devices are mandated wherever backflow risk
exists to protect potable water from contamination.
6. In Michigan code, a building sewer must be at least how many
feet from a private well?
A. 5 feet
B. 10 feet
C. 50 feet
D. 100 feet
Rationale: Michigan plumbing rules require a minimum 50-foot
horizontal separation between sewers and water supply wells.
7. A cleanout is required at a maximum of how many feet in a
straight run of horizontal drainage piping?
A. 50 feet
B. 100 feet
C. 75 feet
D. 150 feet
, Rationale: To allow maintenance, cleanouts are required at
maximum intervals specified by code, often 75 feet.
8. Indirect waste connections are required to be trapped to
prevent:
A. Corrosion
B. Slow drains
C. Sewer gas entry
D. High pH
Rationale: Traps on indirect wastes prevent sewer gas from entering
the building.
9. Fixture units are used for:
A. Water heating calculations
B. Electrical load sizing
C. Sizing of drainage and vent systems
D. Estimating material cost
Rationale: Drainage Fixture Units help determine correct pipe sizes
and capacities.
10. The required potable water supply pressure in Michigan typically
must be at least:
A. 10 psi
B. 20 psi
C. 30 psi
D. 60 psi
Rationale: A minimum 30 psi is generally required at fixtures for
adequate performance.
11. A water service line cannot be smaller than:
A. 3/4 inch
B. 1/4 inch
C. 3/4 inch for single-family residential
D. 2 inches
