Minnesota Subsurface Sewage
Treatment System Inspector Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary purpose of a subsurface sewage treatment system
(SSTS)?
A) To store solid waste indefinitely
B) To treat and disperse wastewater into the soil
C) To incinerate wastewater
D) To recycle potable water directly
Answer: B
Rationale: SSTS systems are designed to treat wastewater through
natural processes and safely disperse it into the soil.
2. Which soil property most directly affects wastewater infiltration rate?
A) Soil color
B) Soil texture
, C) Soil temperature
D) Soil odor
Answer: B
Rationale: Soil texture determines pore size and water movement,
directly influencing infiltration rates.
3. The most critical function of a septic tank is to:
A) Disinfect wastewater
B) Separate solids from liquids
C) Evaporate wastewater
D) Pump effluent to surface water
Answer: B
Rationale: A septic tank primarily allows solids to settle and scum to
float, separating them from liquid effluent.
4. A soil percolation test measures:
A) Soil density
B) Water absorption rate
C) Soil pH
D) Organic content
Answer: B
Rationale: Percolation tests evaluate how quickly water moves
through soil.
5. What is the function of a distribution box in an SSTS?
A) Store sludge
, B) Equalize flow to drainfield laterals
C) Treat wastewater biologically
D) Pump wastewater to the tank
Answer: B
Rationale: It distributes effluent evenly across drainfield lines.
6. The most common type of soil limiting condition is:
A) Excess gravel
B) High permeability
C) Seasonal high water table
D) Excess oxygen
Answer: C
Rationale: A high water table limits soil’s ability to treat and absorb
effluent.
7. Which component is typically found after the septic tank?
A) Building sewer
B) Distribution box
C) Toilet
D) Roof drain
Answer: B
Rationale: The distribution box receives effluent from the septic tank
before the drainfield.
8. Biomat formation in a drainfield primarily:
A) Improves infiltration
, B) Reduces infiltration over time
C) Sterilizes effluent
D) Prevents soil clogging permanently
Answer: B
Rationale: Biomat is a biological layer that gradually restricts flow
into soil.
9. A key indicator of system failure is:
A) Clear effluent at outlet
B) Sewage surfacing in yard
C) Low water usage
D) Dry soil
Answer: B
Rationale: Surface breakout indicates effluent is not being properly
absorbed.
10. Soil structure refers to:
A) Soil mineral type only
B) Arrangement of soil particles into aggregates
C) Soil color patterns
D) Soil depth layers only
Answer: B
Rationale: Structure affects pore spaces and water movement in soil.
11. The minimum separation distance between a septic system and
a well is primarily to prevent:
Treatment System Inspector Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary purpose of a subsurface sewage treatment system
(SSTS)?
A) To store solid waste indefinitely
B) To treat and disperse wastewater into the soil
C) To incinerate wastewater
D) To recycle potable water directly
Answer: B
Rationale: SSTS systems are designed to treat wastewater through
natural processes and safely disperse it into the soil.
2. Which soil property most directly affects wastewater infiltration rate?
A) Soil color
B) Soil texture
, C) Soil temperature
D) Soil odor
Answer: B
Rationale: Soil texture determines pore size and water movement,
directly influencing infiltration rates.
3. The most critical function of a septic tank is to:
A) Disinfect wastewater
B) Separate solids from liquids
C) Evaporate wastewater
D) Pump effluent to surface water
Answer: B
Rationale: A septic tank primarily allows solids to settle and scum to
float, separating them from liquid effluent.
4. A soil percolation test measures:
A) Soil density
B) Water absorption rate
C) Soil pH
D) Organic content
Answer: B
Rationale: Percolation tests evaluate how quickly water moves
through soil.
5. What is the function of a distribution box in an SSTS?
A) Store sludge
, B) Equalize flow to drainfield laterals
C) Treat wastewater biologically
D) Pump wastewater to the tank
Answer: B
Rationale: It distributes effluent evenly across drainfield lines.
6. The most common type of soil limiting condition is:
A) Excess gravel
B) High permeability
C) Seasonal high water table
D) Excess oxygen
Answer: C
Rationale: A high water table limits soil’s ability to treat and absorb
effluent.
7. Which component is typically found after the septic tank?
A) Building sewer
B) Distribution box
C) Toilet
D) Roof drain
Answer: B
Rationale: The distribution box receives effluent from the septic tank
before the drainfield.
8. Biomat formation in a drainfield primarily:
A) Improves infiltration
, B) Reduces infiltration over time
C) Sterilizes effluent
D) Prevents soil clogging permanently
Answer: B
Rationale: Biomat is a biological layer that gradually restricts flow
into soil.
9. A key indicator of system failure is:
A) Clear effluent at outlet
B) Sewage surfacing in yard
C) Low water usage
D) Dry soil
Answer: B
Rationale: Surface breakout indicates effluent is not being properly
absorbed.
10. Soil structure refers to:
A) Soil mineral type only
B) Arrangement of soil particles into aggregates
C) Soil color patterns
D) Soil depth layers only
Answer: B
Rationale: Structure affects pore spaces and water movement in soil.
11. The minimum separation distance between a septic system and
a well is primarily to prevent:
