South Carolina Septic Tank Contractor Exam – EXAM
QUESTIONS AND CORRECT ANSWERS (VERIFIED ANSWERS) PLUS
RATIONALES 2025/2026 Q&A | INSTANT DOWNLOAD PDF
1. What is the primary purpose of a septic tank in a residential wastewater
system?
A. To filter drinking water
B. To store and partially treat wastewater
C. To increase water pressure in plumbing
D. To prevent rainwater from entering the sewer
Correct answer: B. To store and partially treat wastewater – The septic tank holds
wastewater long enough for solids to settle and for anaerobic bacteria to begin
breaking down organic matter.
2. Which material is most commonly used for modern septic tanks?
A. Wood
B. Concrete
C. Plastic
D. Metal
Correct answer: B. Concrete – Concrete is durable, resistant to corrosion, and
widely used for residential septic tanks, although plastic and fiberglass tanks are
also acceptable in some cases.
3. What is the standard minimum distance a septic tank must be installed from a
private well in South Carolina?
A. 10 feet
B. 50 feet
C. 100 feet
D. 200 feet
,Correct answer: C. 100 feet – To protect drinking water from contamination, septic
tanks must be placed at least 100 feet from wells.
4. What is the main function of the drainfield (leach field)?
A. To collect rainwater
B. To evaporate wastewater
C. To disperse effluent into the soil for further treatment
D. To store solids from wastewater
Correct answer: C. To disperse effluent into the soil for further treatment – The
drainfield allows liquid effluent to percolate through soil, where natural processes
remove pathogens and nutrients.
5. Which factor is most critical in determining the size of a septic tank?
A. Roof type
B. Household water usage
C. Soil color
D. Type of plumbing fixtures
Correct answer: B. Household water usage – Tank size is based on the daily
wastewater flow generated by the number of bedrooms or occupants.
6. How often should a residential septic tank typically be pumped?
A. Every 6 months
B. Every 1–3 years
C. Every 10 years
D. Only when it fails
Correct answer: B. Every 1–3 years – Regular pumping prevents solids from
accumulating and clogging the drainfield.
7. What is the purpose of a septic tank baffle?
A. To heat the wastewater
B. To prevent solids from leaving the tank and entering the drainfield
C. To reduce odor
D. To mix wastewater with chemicals
Correct answer: B. To prevent solids from leaving the tank and entering the
drainfield – Baffles direct flow and retain solids to protect the drainfield.
, 8. Which type of soil is most suitable for a drainfield?
A. Clay
B. Sand and loamy soils
C. Solid rock
D. Silt
Correct answer: B. Sand and loamy soils – These soils allow effluent to percolate
effectively while providing filtration for pathogens.
9. What is the typical depth of a residential septic tank inlet and outlet?
A. 6–12 inches below ground
B. 12–36 inches below ground
C. 3–5 feet below ground
D. 6–10 feet below ground
Correct answer: B. 12–36 inches below ground – This depth protects the tank from
freezing, ensures proper gravity flow, and allows for maintenance access.
10. What is the purpose of a riser on a septic tank?
A. To increase tank volume
B. To provide easier access for inspection and pumping
C. To filter effluent
D. To aerate wastewater
Correct answer: B. To provide easier access for inspection and pumping – Risers
bring the tank cover to grade for maintenance convenience.
11. Which of the following can damage a septic system?
A. Excessive water use
B. Disposing of grease or chemicals down drains
C. Planting trees near the drainfield
D. All of the above
Correct answer: D. All of the above – Overloading, chemicals, and root intrusion
can all impair septic system function.
12. In South Carolina, who must approve the installation of a new septic system?
A. The local building inspector
B. South Carolina Department of Health and Environmental Control (DHEC)
QUESTIONS AND CORRECT ANSWERS (VERIFIED ANSWERS) PLUS
RATIONALES 2025/2026 Q&A | INSTANT DOWNLOAD PDF
1. What is the primary purpose of a septic tank in a residential wastewater
system?
A. To filter drinking water
B. To store and partially treat wastewater
C. To increase water pressure in plumbing
D. To prevent rainwater from entering the sewer
Correct answer: B. To store and partially treat wastewater – The septic tank holds
wastewater long enough for solids to settle and for anaerobic bacteria to begin
breaking down organic matter.
2. Which material is most commonly used for modern septic tanks?
A. Wood
B. Concrete
C. Plastic
D. Metal
Correct answer: B. Concrete – Concrete is durable, resistant to corrosion, and
widely used for residential septic tanks, although plastic and fiberglass tanks are
also acceptable in some cases.
3. What is the standard minimum distance a septic tank must be installed from a
private well in South Carolina?
A. 10 feet
B. 50 feet
C. 100 feet
D. 200 feet
,Correct answer: C. 100 feet – To protect drinking water from contamination, septic
tanks must be placed at least 100 feet from wells.
4. What is the main function of the drainfield (leach field)?
A. To collect rainwater
B. To evaporate wastewater
C. To disperse effluent into the soil for further treatment
D. To store solids from wastewater
Correct answer: C. To disperse effluent into the soil for further treatment – The
drainfield allows liquid effluent to percolate through soil, where natural processes
remove pathogens and nutrients.
5. Which factor is most critical in determining the size of a septic tank?
A. Roof type
B. Household water usage
C. Soil color
D. Type of plumbing fixtures
Correct answer: B. Household water usage – Tank size is based on the daily
wastewater flow generated by the number of bedrooms or occupants.
6. How often should a residential septic tank typically be pumped?
A. Every 6 months
B. Every 1–3 years
C. Every 10 years
D. Only when it fails
Correct answer: B. Every 1–3 years – Regular pumping prevents solids from
accumulating and clogging the drainfield.
7. What is the purpose of a septic tank baffle?
A. To heat the wastewater
B. To prevent solids from leaving the tank and entering the drainfield
C. To reduce odor
D. To mix wastewater with chemicals
Correct answer: B. To prevent solids from leaving the tank and entering the
drainfield – Baffles direct flow and retain solids to protect the drainfield.
, 8. Which type of soil is most suitable for a drainfield?
A. Clay
B. Sand and loamy soils
C. Solid rock
D. Silt
Correct answer: B. Sand and loamy soils – These soils allow effluent to percolate
effectively while providing filtration for pathogens.
9. What is the typical depth of a residential septic tank inlet and outlet?
A. 6–12 inches below ground
B. 12–36 inches below ground
C. 3–5 feet below ground
D. 6–10 feet below ground
Correct answer: B. 12–36 inches below ground – This depth protects the tank from
freezing, ensures proper gravity flow, and allows for maintenance access.
10. What is the purpose of a riser on a septic tank?
A. To increase tank volume
B. To provide easier access for inspection and pumping
C. To filter effluent
D. To aerate wastewater
Correct answer: B. To provide easier access for inspection and pumping – Risers
bring the tank cover to grade for maintenance convenience.
11. Which of the following can damage a septic system?
A. Excessive water use
B. Disposing of grease or chemicals down drains
C. Planting trees near the drainfield
D. All of the above
Correct answer: D. All of the above – Overloading, chemicals, and root intrusion
can all impair septic system function.
12. In South Carolina, who must approve the installation of a new septic system?
A. The local building inspector
B. South Carolina Department of Health and Environmental Control (DHEC)
