Minnesota Subsurface Sewage
Treatment System Basic Installer Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. Which soil texture generally provides the best natural treatment for
septic effluent?
A. Clay
B. Sand
C. Loam
D. Gravel
C. Loam
Loam provides balanced drainage and filtration, allowing both
adequate percolation and effective treatment of wastewater before
reaching groundwater.
2. The primary purpose of a septic tank is to:
A. Disinfect wastewater
, B. Store and completely treat sewage
C. Separate solids from liquids
D. Pump effluent to the drainfield
C. Separate solids from liquids
A septic tank allows solids to settle and scum to float while partially
treating wastewater before effluent moves to the soil treatment
system.
3. What is the most important factor in determining drainfield sizing?
A. Household income
B. Soil percolation rate
C. Pipe color
D. Tank shape
B. Soil percolation rate
The soil’s ability to absorb water determines how large the
absorption area must be to safely disperse effluent.
4. Which component distributes effluent evenly in a gravity system?
A. Pump chamber
B. Distribution box
C. Effluent filter
D. Alarm panel
B. Distribution box
A distribution box ensures equal flow of effluent to each trench or
lateral line in the system.
,5. A minimum vertical separation distance is required between a soil
treatment system and:
A. Roof gutters
B. Groundwater
C. Driveways
D. Septic tank lids
B. Groundwater
Separation from groundwater prevents contamination of drinking
water sources and ensures proper treatment in the soil.
6. The scum layer in a septic tank consists mainly of:
A. Heavy solids
B. Oils and grease
C. Sand particles
D. Treated effluent
B. Oils and grease
Fats, oils, and grease float to the top forming the scum layer in the
tank.
7. What is the typical function of an effluent filter?
A. Increase flow rate
B. Remove solids before discharge
C. Disinfect wastewater
D. Measure tank volume
B. Remove solids before discharge
, Effluent filters prevent suspended solids from entering the drainfield,
extending system life.
8. A soil percolation test measures:
A. Tank strength
B. Soil absorption rate
C. Pipe diameter
D. Pump pressure
B. Soil absorption rate
The test determines how quickly water moves through soil to design
an appropriate system.
9. Which condition is most likely to cause system failure?
A. Proper grading
B. Excessive water usage
C. Routine maintenance
D. Adequate soil depth
B. Excessive water usage
Overloading the system exceeds soil and tank capacity, leading to
surfacing effluent or backups.
10. The purpose of a septic tank baffle is to:
A. Increase oxygen levels
B. Direct flow and prevent solids escape
C. Pump effluent
D. Measure sludge depth
Treatment System Basic Installer Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. Which soil texture generally provides the best natural treatment for
septic effluent?
A. Clay
B. Sand
C. Loam
D. Gravel
C. Loam
Loam provides balanced drainage and filtration, allowing both
adequate percolation and effective treatment of wastewater before
reaching groundwater.
2. The primary purpose of a septic tank is to:
A. Disinfect wastewater
, B. Store and completely treat sewage
C. Separate solids from liquids
D. Pump effluent to the drainfield
C. Separate solids from liquids
A septic tank allows solids to settle and scum to float while partially
treating wastewater before effluent moves to the soil treatment
system.
3. What is the most important factor in determining drainfield sizing?
A. Household income
B. Soil percolation rate
C. Pipe color
D. Tank shape
B. Soil percolation rate
The soil’s ability to absorb water determines how large the
absorption area must be to safely disperse effluent.
4. Which component distributes effluent evenly in a gravity system?
A. Pump chamber
B. Distribution box
C. Effluent filter
D. Alarm panel
B. Distribution box
A distribution box ensures equal flow of effluent to each trench or
lateral line in the system.
,5. A minimum vertical separation distance is required between a soil
treatment system and:
A. Roof gutters
B. Groundwater
C. Driveways
D. Septic tank lids
B. Groundwater
Separation from groundwater prevents contamination of drinking
water sources and ensures proper treatment in the soil.
6. The scum layer in a septic tank consists mainly of:
A. Heavy solids
B. Oils and grease
C. Sand particles
D. Treated effluent
B. Oils and grease
Fats, oils, and grease float to the top forming the scum layer in the
tank.
7. What is the typical function of an effluent filter?
A. Increase flow rate
B. Remove solids before discharge
C. Disinfect wastewater
D. Measure tank volume
B. Remove solids before discharge
, Effluent filters prevent suspended solids from entering the drainfield,
extending system life.
8. A soil percolation test measures:
A. Tank strength
B. Soil absorption rate
C. Pipe diameter
D. Pump pressure
B. Soil absorption rate
The test determines how quickly water moves through soil to design
an appropriate system.
9. Which condition is most likely to cause system failure?
A. Proper grading
B. Excessive water usage
C. Routine maintenance
D. Adequate soil depth
B. Excessive water usage
Overloading the system exceeds soil and tank capacity, leading to
surfacing effluent or backups.
10. The purpose of a septic tank baffle is to:
A. Increase oxygen levels
B. Direct flow and prevent solids escape
C. Pump effluent
D. Measure sludge depth
