Onsite Wastewater System Installer
Licensing Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
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1. A primary function of a septic tank in an onsite wastewater system is
to:
A. Evaporate all wastewater
B. Filter wastewater using sand
C. Allow solids to settle and begin biological breakdown
D. Pump effluent to drinking water supplies
Rationale: Septic tanks are designed for primary treatment,
separating solids (sludge/scum) from liquid effluent for further
treatment.
2. The soil treatment area primarily:
A. Increases wastewater flow
, B. Removes pathogens and nutrients
C. Absorbs and treats effluent
D. Stores wastewater long-term
Rationale: Soil provides natural filtration and biological treatment of
effluent as it percolates.
3. Which component conveys effluent from the septic tank to the soil
absorption field?
A. Inspection ports
B. Distribution box
C. Effluent filter
D. Sewage ejector pump
Rationale: A distribution box evenly distributes effluent to multiple
trenches or laterals.
4. The scum layer in a septic tank consists mostly of:
A. Inorganic solids
B. Sand and grit
C. Fats, oils, and grease
D. Fully treated water
Rationale: FOG floats to the top creating a scum layer requiring
maintenance.
5. What is the minimum separation typically required between a septic
drainfield and a private well (varies by jurisdiction)?
A. 10 feet
, B. 25 feet
C. 50–100 feet
D. 300 feet
Rationale: Well setbacks prevent groundwater contamination from
effluent; most codes require 50–100 ft.
6. Hydraulic loading rate of soil refers to:
A. Soil nutrient content
B. The amount of effluent soil can receive per area per day
C. Soil air-exchange rate
D. Soil acidity level
Rationale: Determines system sizing based on infiltration capacity.
7. Percolation testing measures:
A. Soil alkalinity
B. Organic content
C. Water infiltration rate
D. Groundwater hardness
Rationale: Percolation tests show how quickly soil absorbs water,
essential for design.
8. Pump chambers are used when:
A. Effluent can flow downhill by gravity
B. Elevation prevents gravity flow to the field
C. The tank is too large
D. Drinking water must be pumped
Licensing Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. A primary function of a septic tank in an onsite wastewater system is
to:
A. Evaporate all wastewater
B. Filter wastewater using sand
C. Allow solids to settle and begin biological breakdown
D. Pump effluent to drinking water supplies
Rationale: Septic tanks are designed for primary treatment,
separating solids (sludge/scum) from liquid effluent for further
treatment.
2. The soil treatment area primarily:
A. Increases wastewater flow
, B. Removes pathogens and nutrients
C. Absorbs and treats effluent
D. Stores wastewater long-term
Rationale: Soil provides natural filtration and biological treatment of
effluent as it percolates.
3. Which component conveys effluent from the septic tank to the soil
absorption field?
A. Inspection ports
B. Distribution box
C. Effluent filter
D. Sewage ejector pump
Rationale: A distribution box evenly distributes effluent to multiple
trenches or laterals.
4. The scum layer in a septic tank consists mostly of:
A. Inorganic solids
B. Sand and grit
C. Fats, oils, and grease
D. Fully treated water
Rationale: FOG floats to the top creating a scum layer requiring
maintenance.
5. What is the minimum separation typically required between a septic
drainfield and a private well (varies by jurisdiction)?
A. 10 feet
, B. 25 feet
C. 50–100 feet
D. 300 feet
Rationale: Well setbacks prevent groundwater contamination from
effluent; most codes require 50–100 ft.
6. Hydraulic loading rate of soil refers to:
A. Soil nutrient content
B. The amount of effluent soil can receive per area per day
C. Soil air-exchange rate
D. Soil acidity level
Rationale: Determines system sizing based on infiltration capacity.
7. Percolation testing measures:
A. Soil alkalinity
B. Organic content
C. Water infiltration rate
D. Groundwater hardness
Rationale: Percolation tests show how quickly soil absorbs water,
essential for design.
8. Pump chambers are used when:
A. Effluent can flow downhill by gravity
B. Elevation prevents gravity flow to the field
C. The tank is too large
D. Drinking water must be pumped
