Onsite Wastewater System Installer
Licensing Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A Instant Download
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1. What is the primary purpose of an onsite wastewater treatment system?
a) To generate electricity
b) To store water
c) To treat and dispose of wastewater safely
d) To filter drinking water
Rationale: The main goal of an onsite system is to treat wastewater so it
can safely enter the environment without causing pollution or health
hazards.
2. Which component of a conventional septic system stores solids while
allowing liquids to flow out?
a) Septic tank
b) Distribution box
c) Drainfield
d) Sand filter
Rationale: The septic tank retains solids for decomposition and allows
clarified effluent to flow to the drainfield.
,3. What type of soil is best suited for a standard drainfield?
a) Clay
b) Sandy loam
c) Silt
d) Heavy clay
Rationale: Sandy loam provides adequate percolation and filtration,
ensuring proper effluent absorption.
4. What is the minimum separation required between a septic tank and a
water well?
a) 10 feet
b) 25 feet
c) 50 feet
d) 100 feet
Rationale: Regulatory standards typically require at least 50 feet to
prevent contamination of drinking water sources.
5. Which method is used to determine soil percolation rate for a drainfield?
a) Pump test
b) Perc test
c) Soil boring
d) Infiltration test
Rationale: A perc (percolation) test measures how quickly soil absorbs
water, essential for drainfield sizing.
6. What is the function of a distribution box in a septic system?
a) Store solids
b) Evenly distribute effluent to drainfield lines
c) Pump wastewater to a treatment plant
d) Aerate wastewater
Rationale: The distribution box ensures that effluent flows evenly into
multiple drainfield trenches.
7. Which type of system is used in areas with shallow soil over bedrock?
a) Conventional septic
, b) Mound system
c) At-grade system
d) Lagoon system
Rationale: At-grade systems are designed for shallow soils and high water
tables, elevating the absorption area above the ground.
8. What is the typical minimum slope for effluent piping from a septic tank to
a drainfield?
a) 1%
b) 2%
c) 5%
d) 10%
Rationale: A 2% slope ensures gravity flow while preventing solids from
settling in the pipe.
9. Which of the following is considered a suitable alternative for conventional
drainfields in poor soils?
a) Concrete pit
b) Sand mound
c) Pressure-dosed system
d) Open pond
Rationale: Pressure-dosed systems can distribute effluent evenly over
restrictive soils where gravity flow is insufficient.
10.What is the minimum liquid capacity of a septic tank for a three-bedroom
house?
a) 500 gallons
b) 1000 gallons
c) 1500 gallons
d) 2000 gallons
Rationale: Standard guidelines require approximately 1000 gallons for a
typical three-bedroom home to handle daily wastewater flows.
11.How often should a septic tank typically be pumped?
a) Every 6 months
Licensing Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A Instant Download
1. What is the primary purpose of an onsite wastewater treatment system?
a) To generate electricity
b) To store water
c) To treat and dispose of wastewater safely
d) To filter drinking water
Rationale: The main goal of an onsite system is to treat wastewater so it
can safely enter the environment without causing pollution or health
hazards.
2. Which component of a conventional septic system stores solids while
allowing liquids to flow out?
a) Septic tank
b) Distribution box
c) Drainfield
d) Sand filter
Rationale: The septic tank retains solids for decomposition and allows
clarified effluent to flow to the drainfield.
,3. What type of soil is best suited for a standard drainfield?
a) Clay
b) Sandy loam
c) Silt
d) Heavy clay
Rationale: Sandy loam provides adequate percolation and filtration,
ensuring proper effluent absorption.
4. What is the minimum separation required between a septic tank and a
water well?
a) 10 feet
b) 25 feet
c) 50 feet
d) 100 feet
Rationale: Regulatory standards typically require at least 50 feet to
prevent contamination of drinking water sources.
5. Which method is used to determine soil percolation rate for a drainfield?
a) Pump test
b) Perc test
c) Soil boring
d) Infiltration test
Rationale: A perc (percolation) test measures how quickly soil absorbs
water, essential for drainfield sizing.
6. What is the function of a distribution box in a septic system?
a) Store solids
b) Evenly distribute effluent to drainfield lines
c) Pump wastewater to a treatment plant
d) Aerate wastewater
Rationale: The distribution box ensures that effluent flows evenly into
multiple drainfield trenches.
7. Which type of system is used in areas with shallow soil over bedrock?
a) Conventional septic
, b) Mound system
c) At-grade system
d) Lagoon system
Rationale: At-grade systems are designed for shallow soils and high water
tables, elevating the absorption area above the ground.
8. What is the typical minimum slope for effluent piping from a septic tank to
a drainfield?
a) 1%
b) 2%
c) 5%
d) 10%
Rationale: A 2% slope ensures gravity flow while preventing solids from
settling in the pipe.
9. Which of the following is considered a suitable alternative for conventional
drainfields in poor soils?
a) Concrete pit
b) Sand mound
c) Pressure-dosed system
d) Open pond
Rationale: Pressure-dosed systems can distribute effluent evenly over
restrictive soils where gravity flow is insufficient.
10.What is the minimum liquid capacity of a septic tank for a three-bedroom
house?
a) 500 gallons
b) 1000 gallons
c) 1500 gallons
d) 2000 gallons
Rationale: Standard guidelines require approximately 1000 gallons for a
typical three-bedroom home to handle daily wastewater flows.
11.How often should a septic tank typically be pumped?
a) Every 6 months
