TEXAS OSSF INSTALLER 1 LICENSE EXAM / ACTUAL EXAM
QUESTIONS AND CORRECT ANSWERS WITH RATIONALES
GRADED A+ LATEST 2026
1. The primary purpose of an On-Site Sewage Facility (OSSF) is to:
A. Store wastewater for later disposal
B. Treat and dispose of household wastewater safely on the property
C. Pump wastewater to a nearby creek
D. Evaporate wastewater into the atmosphere
Answer: B
Rationale: An OSSF’s main goal is to treat and dispose of wastewater
safely and effectively on-site, protecting both public health and
groundwater.
2. Before beginning any installation, the installer must:
A. Get verbal consent from the property owner
B. Obtain an approved permit from the local permitting authority
C. Install the system and submit paperwork later
D. Only notify the local health department
Answer: B
Rationale: Permitting is mandatory under Texas regulations before any
installation or alteration of an OSSF system.
3. The first step in selecting an appropriate OSSF system is:
A. Choosing the least expensive design
B. Conducting a soil and site evaluation
C. Measuring the tank size
D. Installing trenches before testing
,Answer: B
Rationale: Soil and site evaluations determine percolation, slope, and
restrictive horizons — all critical for proper design.
4. The percolation test measures:
A. Water color
B. Soil infiltration rate
C. Effluent pH
D. Tank leakage
Answer: B
Rationale: Percolation tests assess how quickly water moves through
soil, helping determine trench length and loading rate.
5. What is the minimum required setback between a septic tank
and a private water well?
A. 25 feet
B. 50 feet
C. 75 feet
D. 100 feet
Answer: D
Rationale: Texas rules mandate a minimum 100-foot separation to
protect groundwater quality.
6. A conventional OSSF system typically includes:
A. A holding tank only
B. A septic tank and a drain field
C. A chlorine contact chamber
, D. A sand filter
Answer: B
Rationale: Standard systems include a septic tank for treatment and a
soil absorption field for disposal.
7. The separation distance between the bottom of a trench and the
groundwater table must be at least:
A. 6 inches
B. 12 inches
C. 24 inches
D. 36 inches
Answer: C
Rationale: A 2-foot unsaturated zone is required for proper aerobic
treatment of effluent in the soil.
8.The minimum liquid capacity for a septic tank serving a 3-
bedroom residence is:
• A. 750 gallons
• B. 1,000 gallons
• C. 1,250 gallons
• D. 1,500 gallons
Answer: B
Rationale: Texas regulations require a minimum 1,000-gallon tank for a
3-bedroom home to provide adequate settling and treatment time for
household wastewater.
, 9.Installer I license holders are authorized to install:
• A. All OSSF systems including aerobic treatment units
• B. Standard conventional systems such as septic tanks and absorptive
drain fields
• C. Only maintenance on existing systems
• D. Spray irrigation systems only
Answer: B
Rationale: Installer I is limited to standard systems; Installer II is
required for non-standard or advanced systems such as aerobic
treatment units.
10.The minimum setback distance from a septic tank or absorption
field to the property line is generally:
• A. 2 feet
• B. 5 feet
• C. 10 feet
• D. 25 feet
Answer: B
Rationale: Texas OSSF rules require at least 5 feet from property lines
to prevent contamination of adjacent properties.
11.What is the purpose of the baffle or tee in a septic tank?
• A. To increase storage capacity
• B. To prevent solids from entering the outlet pipe
QUESTIONS AND CORRECT ANSWERS WITH RATIONALES
GRADED A+ LATEST 2026
1. The primary purpose of an On-Site Sewage Facility (OSSF) is to:
A. Store wastewater for later disposal
B. Treat and dispose of household wastewater safely on the property
C. Pump wastewater to a nearby creek
D. Evaporate wastewater into the atmosphere
Answer: B
Rationale: An OSSF’s main goal is to treat and dispose of wastewater
safely and effectively on-site, protecting both public health and
groundwater.
2. Before beginning any installation, the installer must:
A. Get verbal consent from the property owner
B. Obtain an approved permit from the local permitting authority
C. Install the system and submit paperwork later
D. Only notify the local health department
Answer: B
Rationale: Permitting is mandatory under Texas regulations before any
installation or alteration of an OSSF system.
3. The first step in selecting an appropriate OSSF system is:
A. Choosing the least expensive design
B. Conducting a soil and site evaluation
C. Measuring the tank size
D. Installing trenches before testing
,Answer: B
Rationale: Soil and site evaluations determine percolation, slope, and
restrictive horizons — all critical for proper design.
4. The percolation test measures:
A. Water color
B. Soil infiltration rate
C. Effluent pH
D. Tank leakage
Answer: B
Rationale: Percolation tests assess how quickly water moves through
soil, helping determine trench length and loading rate.
5. What is the minimum required setback between a septic tank
and a private water well?
A. 25 feet
B. 50 feet
C. 75 feet
D. 100 feet
Answer: D
Rationale: Texas rules mandate a minimum 100-foot separation to
protect groundwater quality.
6. A conventional OSSF system typically includes:
A. A holding tank only
B. A septic tank and a drain field
C. A chlorine contact chamber
, D. A sand filter
Answer: B
Rationale: Standard systems include a septic tank for treatment and a
soil absorption field for disposal.
7. The separation distance between the bottom of a trench and the
groundwater table must be at least:
A. 6 inches
B. 12 inches
C. 24 inches
D. 36 inches
Answer: C
Rationale: A 2-foot unsaturated zone is required for proper aerobic
treatment of effluent in the soil.
8.The minimum liquid capacity for a septic tank serving a 3-
bedroom residence is:
• A. 750 gallons
• B. 1,000 gallons
• C. 1,250 gallons
• D. 1,500 gallons
Answer: B
Rationale: Texas regulations require a minimum 1,000-gallon tank for a
3-bedroom home to provide adequate settling and treatment time for
household wastewater.
, 9.Installer I license holders are authorized to install:
• A. All OSSF systems including aerobic treatment units
• B. Standard conventional systems such as septic tanks and absorptive
drain fields
• C. Only maintenance on existing systems
• D. Spray irrigation systems only
Answer: B
Rationale: Installer I is limited to standard systems; Installer II is
required for non-standard or advanced systems such as aerobic
treatment units.
10.The minimum setback distance from a septic tank or absorption
field to the property line is generally:
• A. 2 feet
• B. 5 feet
• C. 10 feet
• D. 25 feet
Answer: B
Rationale: Texas OSSF rules require at least 5 feet from property lines
to prevent contamination of adjacent properties.
11.What is the purpose of the baffle or tee in a septic tank?
• A. To increase storage capacity
• B. To prevent solids from entering the outlet pipe
