AZ A-12 Sewers, Drains & Pipe Laying
Contractor Exam Questions and Correct
Answers (Verified Answers) Plus Rationale
2027 Q&A| Instant Download Pdf
1. What is the primary purpose of a sanitary sewer system?
a. To transport stormwater from streets
b. To provide drinking water to buildings
c. To transport wastewater to a treatment or disposal facility
d. To increase groundwater recharge
Answer: c. To transport wastewater to a treatment or disposal facility
Rationale: A sanitary sewer system collects wastewater from
buildings and other approved sources and conveys it to a treatment
plant or other authorized disposal facility. Stormwater is generally
handled by a separate drainage system.
, 2. When laying gravity sewer pipe, what is the most important factor
for maintaining proper flow?
a. Pipe color
b. Proper grade
c. Pipe wall thickness alone
d. Manhole diameter
Answer: b. Proper grade
Rationale: Gravity sewers depend on elevation differences to move
wastewater. Maintaining the specified slope provides sufficient
hydraulic gradient for flow while helping prevent sediment from
settling in the pipe.
3. What instrument is commonly used to establish and check
elevations during sewer pipe installation?
a. Pipe wrench
b. Level or laser level
c. Pressure gauge
d. Torque wrench
Answer: b. Level or laser level
,Rationale: A level, rotary laser, or pipe laser can establish the
designed elevation and grade of a sewer line. Accurate elevation
control is essential because even small deviations can affect gravity
flow.
4. What is the primary function of a sewer manhole?
a. Increase water pressure
b. Provide access for inspection, cleaning, and maintenance
c. Filter wastewater
d. Prevent all groundwater infiltration
Answer: b. Provide access for inspection, cleaning, and maintenance
Rationale: Manholes provide personnel and equipment access to
underground sewer lines. They are commonly placed at changes in
direction, grade, pipe size, or junctions and at other locations required
by the design.
5. Before excavation begins, what should a contractor do regarding
underground utilities?
a. Assume utility locations from old drawings
b. Begin excavation slowly without notifying anyone
, c. Have underground utilities located and marked
d. Remove all utility markings from the site
Answer: c. Have underground utilities located and marked
Rationale: Underground utility locating is a critical pre-excavation
activity. Identifying and marking existing utilities reduces the risk of
striking electrical, gas, water, communication, or other buried
infrastructure.
6. What is the purpose of bedding beneath a sewer pipe?
a. To increase wastewater temperature
b. To provide uniform support for the pipe
c. To eliminate the need for compaction
d. To increase pipe pressure
Answer: b. To provide uniform support for the pipe
Rationale: Proper bedding distributes loads and provides continuous
support beneath the pipe. Poor bedding can result in point loading,
settlement, pipe deformation, joint problems, and loss of grade.
7. What should generally be avoided when preparing the bottom of
a sewer trench?
Contractor Exam Questions and Correct
Answers (Verified Answers) Plus Rationale
2027 Q&A| Instant Download Pdf
1. What is the primary purpose of a sanitary sewer system?
a. To transport stormwater from streets
b. To provide drinking water to buildings
c. To transport wastewater to a treatment or disposal facility
d. To increase groundwater recharge
Answer: c. To transport wastewater to a treatment or disposal facility
Rationale: A sanitary sewer system collects wastewater from
buildings and other approved sources and conveys it to a treatment
plant or other authorized disposal facility. Stormwater is generally
handled by a separate drainage system.
, 2. When laying gravity sewer pipe, what is the most important factor
for maintaining proper flow?
a. Pipe color
b. Proper grade
c. Pipe wall thickness alone
d. Manhole diameter
Answer: b. Proper grade
Rationale: Gravity sewers depend on elevation differences to move
wastewater. Maintaining the specified slope provides sufficient
hydraulic gradient for flow while helping prevent sediment from
settling in the pipe.
3. What instrument is commonly used to establish and check
elevations during sewer pipe installation?
a. Pipe wrench
b. Level or laser level
c. Pressure gauge
d. Torque wrench
Answer: b. Level or laser level
,Rationale: A level, rotary laser, or pipe laser can establish the
designed elevation and grade of a sewer line. Accurate elevation
control is essential because even small deviations can affect gravity
flow.
4. What is the primary function of a sewer manhole?
a. Increase water pressure
b. Provide access for inspection, cleaning, and maintenance
c. Filter wastewater
d. Prevent all groundwater infiltration
Answer: b. Provide access for inspection, cleaning, and maintenance
Rationale: Manholes provide personnel and equipment access to
underground sewer lines. They are commonly placed at changes in
direction, grade, pipe size, or junctions and at other locations required
by the design.
5. Before excavation begins, what should a contractor do regarding
underground utilities?
a. Assume utility locations from old drawings
b. Begin excavation slowly without notifying anyone
, c. Have underground utilities located and marked
d. Remove all utility markings from the site
Answer: c. Have underground utilities located and marked
Rationale: Underground utility locating is a critical pre-excavation
activity. Identifying and marking existing utilities reduces the risk of
striking electrical, gas, water, communication, or other buried
infrastructure.
6. What is the purpose of bedding beneath a sewer pipe?
a. To increase wastewater temperature
b. To provide uniform support for the pipe
c. To eliminate the need for compaction
d. To increase pipe pressure
Answer: b. To provide uniform support for the pipe
Rationale: Proper bedding distributes loads and provides continuous
support beneath the pipe. Poor bedding can result in point loading,
settlement, pipe deformation, joint problems, and loss of grade.
7. What should generally be avoided when preparing the bottom of
a sewer trench?
