Texas On-Site Sewage Facility (OSSF) Installer II
License Examination Practice Questions and Verified
Answers (With Rationales)2026–2028 Q&A | Instant
Download PDF
About This Exam
This practice exam is designed for individuals preparing for the Texas OSSF Installer II
License Examination administered by the Texas Commission on Environmental Quality
(TCEQ) . An Installer II license authorizes the holder to construct all types of on-site
sewage facilities, making it the advanced level of installer certification in Texas .
Section 1: Basic System Components & Functions (Questions 1–20)
1. Which of the following is the primary purpose of a septic tank in an onsite sewage
facility?
A. To distribute effluent evenly across the drainfield
B. To treat effluent to drinking water standards
C. To separate solids from liquids
D. To disinfect wastewater before discharge
Answer: C
Rationale: : The septic tank primarily separates solids from liquids, allowing solids to settle
as sludge at the bottom and lighter materials (scum) to rise to the top. This begins the
treatment process before effluent flows to the soil absorption system .
2. What is the minimum liquid capacity of a septic tank for a typical single-family
home in Texas?
,A. 500 gallons
B. 750 gallons
C. 1,000 gallons
D. 1,500 gallons
Answer: C
*Rationale: : TCEQ rules generally require a minimum 1,000-gallon septic tank for single-
family dwellings to handle typical wastewater flow based on the number of bedrooms .*
3. How often should a septic tank generally be pumped to prevent solids from
entering the drainfield?
A. Every 6 months
B. Every 3–5 years
C. Every 10 years
D. Only when it backs up
Answer: B
Rationale: : Pumping every 3–5 years is standard practice to prevent accumulated solids
from clogging the soil absorption system and causing premature failure .
4. What type of soil is most suitable for a conventional drainfield?
A. Sandy soil
B. Loamy soil
C. Clay soil
D. Rocky soil
Answer: B
Rationale: : Loamy soil provides the optimal balance of good drainage and filtering
capacity, making it ideal for a conventional drainfield. It allows adequate percolation while
still providing treatment .
,5. What is the primary cause of premature failure in a soil absorption system?
A. Overuse of household disinfectants
B. Improper tank lid placement
C. Excessive solids in the drainfield
D. Low water usage
Answer: C
Rationale: : When solids escape the septic tank and enter the drainfield, they clog soil
pores, leading to hydraulic failure and system failure .
6. What is the minimum separation distance between a septic tank and a private
water well in Texas?
A. 25 feet
B. 50 feet
C. 100 feet
D. 200 feet
Answer: C
*Rationale: : Texas regulations require a minimum 100-foot distance between a private
water well and any component of an OSSF system to prevent contamination of the water
supply .*
7. Which of the following materials is commonly approved for septic tank
construction in Texas?
A. Wood
B. Concrete
C. Aluminum
D. Glass
, Answer: B
Rationale: : Concrete is durable, watertight, and commonly approved for septic tank
construction. Other approved materials include fiberglass and polyethylene .
8. Which device is used to measure the flow rate into a septic tank during testing?
A. Pressure gauge
B. Flow meter
C. Soil probe
D. pH meter
Answer: B
Rationale: : A flow meter is used to quantify wastewater entering the tank for design and
testing purposes .
9. What is the main function of the baffle in a septic tank?
A. To increase tank capacity
B. To aerate wastewater
C. To prevent solids from exiting the tank
D. To filter bacteria
Answer: C
Rationale: : Baffles direct flow and keep solids in the tank while allowing clarified effluent to
exit. They prevent scum and sludge from leaving the tank .
10. Pits constructed in permeable soil with open-jointed material that receive direct
discharge of raw wastewater are called:
License Examination Practice Questions and Verified
Answers (With Rationales)2026–2028 Q&A | Instant
Download PDF
About This Exam
This practice exam is designed for individuals preparing for the Texas OSSF Installer II
License Examination administered by the Texas Commission on Environmental Quality
(TCEQ) . An Installer II license authorizes the holder to construct all types of on-site
sewage facilities, making it the advanced level of installer certification in Texas .
Section 1: Basic System Components & Functions (Questions 1–20)
1. Which of the following is the primary purpose of a septic tank in an onsite sewage
facility?
A. To distribute effluent evenly across the drainfield
B. To treat effluent to drinking water standards
C. To separate solids from liquids
D. To disinfect wastewater before discharge
Answer: C
Rationale: : The septic tank primarily separates solids from liquids, allowing solids to settle
as sludge at the bottom and lighter materials (scum) to rise to the top. This begins the
treatment process before effluent flows to the soil absorption system .
2. What is the minimum liquid capacity of a septic tank for a typical single-family
home in Texas?
,A. 500 gallons
B. 750 gallons
C. 1,000 gallons
D. 1,500 gallons
Answer: C
*Rationale: : TCEQ rules generally require a minimum 1,000-gallon septic tank for single-
family dwellings to handle typical wastewater flow based on the number of bedrooms .*
3. How often should a septic tank generally be pumped to prevent solids from
entering the drainfield?
A. Every 6 months
B. Every 3–5 years
C. Every 10 years
D. Only when it backs up
Answer: B
Rationale: : Pumping every 3–5 years is standard practice to prevent accumulated solids
from clogging the soil absorption system and causing premature failure .
4. What type of soil is most suitable for a conventional drainfield?
A. Sandy soil
B. Loamy soil
C. Clay soil
D. Rocky soil
Answer: B
Rationale: : Loamy soil provides the optimal balance of good drainage and filtering
capacity, making it ideal for a conventional drainfield. It allows adequate percolation while
still providing treatment .
,5. What is the primary cause of premature failure in a soil absorption system?
A. Overuse of household disinfectants
B. Improper tank lid placement
C. Excessive solids in the drainfield
D. Low water usage
Answer: C
Rationale: : When solids escape the septic tank and enter the drainfield, they clog soil
pores, leading to hydraulic failure and system failure .
6. What is the minimum separation distance between a septic tank and a private
water well in Texas?
A. 25 feet
B. 50 feet
C. 100 feet
D. 200 feet
Answer: C
*Rationale: : Texas regulations require a minimum 100-foot distance between a private
water well and any component of an OSSF system to prevent contamination of the water
supply .*
7. Which of the following materials is commonly approved for septic tank
construction in Texas?
A. Wood
B. Concrete
C. Aluminum
D. Glass
, Answer: B
Rationale: : Concrete is durable, watertight, and commonly approved for septic tank
construction. Other approved materials include fiberglass and polyethylene .
8. Which device is used to measure the flow rate into a septic tank during testing?
A. Pressure gauge
B. Flow meter
C. Soil probe
D. pH meter
Answer: B
Rationale: : A flow meter is used to quantify wastewater entering the tank for design and
testing purposes .
9. What is the main function of the baffle in a septic tank?
A. To increase tank capacity
B. To aerate wastewater
C. To prevent solids from exiting the tank
D. To filter bacteria
Answer: C
Rationale: : Baffles direct flow and keep solids in the tank while allowing clarified effluent to
exit. They prevent scum and sludge from leaving the tank .
10. Pits constructed in permeable soil with open-jointed material that receive direct
discharge of raw wastewater are called:
