Onsite Wastewater System Installer Licensing
Exam Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary purpose of an onsite wastewater system?
a) To supply drinking water
b) To treat and dispose of household wastewater
c) To irrigate lawns
d) To store stormwater
The main goal of an onsite wastewater system is to safely treat
and dispose of domestic wastewater on-site.
2. Which component of a septic system distributes effluent evenly to
the drainfield?
a) Septic tank
b) Distribution box
c) Pump chamber
d) Vent stack
The distribution box ensures effluent is evenly distributed to all
trenches of the drainfield.
3. What is the minimum recommended distance between a septic
tank and a potable water well?
a) 10 feet
b) 25 feet
c) 50 feet
, d) 100 feet
Local regulations typically require a minimum distance of 100 feet
to prevent contamination of drinking water.
4. Which soil property most affects percolation rate in a drainfield?
a) Color
b) Texture
c) Porosity and permeability
d) Temperature
Soil porosity and permeability determine how quickly effluent can
move through the soil for treatment.
5. What type of soil is generally least suitable for a conventional
septic drainfield?
a) Sandy soil
b) Gravelly soil
c) Clay soil
d) Loamy soil
Clay soil drains slowly and can cause effluent backup and system
failure.
6. What is the typical first step when installing a new septic tank?
a) Install the drainfield
b) Connect the effluent line
c) Excavate the tank location
d) Backfill the trench
Excavation is the first step to properly position the tank according
to design specifications.
7. Which of the following can cause premature failure of a septic
drainfield?
, a) Regular pumping
b) Planting grass over the drainfield
c) Excessive water use and soil compaction
d) Proper sizing of the system
Overloading the system with water or compacting the soil can
reduce absorption and lead to failure.
8. How often should a typical septic tank be pumped?
a) Every year
b) Every 2–3 years
c) Every 3–5 years
d) Every 10 years
Pumping every 3–5 years removes accumulated solids and
prevents clogging the drainfield.
9. What is the purpose of the baffle in a septic tank?
a) To aerate effluent
b) To distribute effluent to the drainfield
c) To prevent solids from leaving the tank
d) To vent gases
Baffles help keep solids in the tank while allowing clarified effluent
to exit.
10. Which material is most commonly used for septic tanks?
a) Wood
b) Concrete
c) Plastic
d) Steel
Concrete is durable and resistant to soil and wastewater
conditions, making it the most common material.
Exam Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary purpose of an onsite wastewater system?
a) To supply drinking water
b) To treat and dispose of household wastewater
c) To irrigate lawns
d) To store stormwater
The main goal of an onsite wastewater system is to safely treat
and dispose of domestic wastewater on-site.
2. Which component of a septic system distributes effluent evenly to
the drainfield?
a) Septic tank
b) Distribution box
c) Pump chamber
d) Vent stack
The distribution box ensures effluent is evenly distributed to all
trenches of the drainfield.
3. What is the minimum recommended distance between a septic
tank and a potable water well?
a) 10 feet
b) 25 feet
c) 50 feet
, d) 100 feet
Local regulations typically require a minimum distance of 100 feet
to prevent contamination of drinking water.
4. Which soil property most affects percolation rate in a drainfield?
a) Color
b) Texture
c) Porosity and permeability
d) Temperature
Soil porosity and permeability determine how quickly effluent can
move through the soil for treatment.
5. What type of soil is generally least suitable for a conventional
septic drainfield?
a) Sandy soil
b) Gravelly soil
c) Clay soil
d) Loamy soil
Clay soil drains slowly and can cause effluent backup and system
failure.
6. What is the typical first step when installing a new septic tank?
a) Install the drainfield
b) Connect the effluent line
c) Excavate the tank location
d) Backfill the trench
Excavation is the first step to properly position the tank according
to design specifications.
7. Which of the following can cause premature failure of a septic
drainfield?
, a) Regular pumping
b) Planting grass over the drainfield
c) Excessive water use and soil compaction
d) Proper sizing of the system
Overloading the system with water or compacting the soil can
reduce absorption and lead to failure.
8. How often should a typical septic tank be pumped?
a) Every year
b) Every 2–3 years
c) Every 3–5 years
d) Every 10 years
Pumping every 3–5 years removes accumulated solids and
prevents clogging the drainfield.
9. What is the purpose of the baffle in a septic tank?
a) To aerate effluent
b) To distribute effluent to the drainfield
c) To prevent solids from leaving the tank
d) To vent gases
Baffles help keep solids in the tank while allowing clarified effluent
to exit.
10. Which material is most commonly used for septic tanks?
a) Wood
b) Concrete
c) Plastic
d) Steel
Concrete is durable and resistant to soil and wastewater
conditions, making it the most common material.
