TCEQ OSSF LICENSE EXAM STUDY GUIDE | COMPLETE 2026/2027 PREP |250 VERIFIED
QUESTIONS, MATH FORMULAS, & SITE EVALUATION ANSWERS | 100% GUARANTEED
PASS!!!
1. A site has deep, permeable clay loam over fractured bedrock at 18 inches. Which system is prohibited?
A) Low-pressure pipe
B) Evapotranspiration bed
C) Conventional trench with 24″ depth
D) Drip dispersal with pretreatment
Answer: C
Trenches require 24″ of suitable soil below trench bottom; fractured bedrock at 18″ fails separation requirement.
2. During a perc test, water drops 1 inch in 20 minutes. What is the perc rate in minutes per inch?
A) 10 min/in
B) 20 min/in
C) 30 min/in
D) 40 min/in
Answer: B
Perc rate = minutes ÷ inches dropped = 20 min/1 inch = 20 min/in.
3. A site has 40% slope. Which system is NOT allowed without major modification?
A) Spray irrigation
B) Drip dispersal
C) Conventional trench
D) At-grade system
Answer: C
Conventional trenches limited to <15% slope; 40% requires pressure-dosed or drip systems.
4. You measure 12 inches of loamy sand over 6 inches of clay. What is the limiting layer?
A) Loamy sand
B) Clay
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,C) The interface
D) Groundwater
Answer: B
Clay acts as a limiting layer due to low permeability, regardless of depth.
5. A homeowner wants an OSSF within 50 feet of a stream. What is required?
A) 200% sizing increase
B) Advanced treatment (Type II)
C) No OSSF allowed
D) Only a septic tank
Answer: B
Within 50–100 ft of surface water, Type II treatment (≤10 mg/L BOD/TSS) mandatory.
6. Daily flow for a 4-bedroom house in TCEQ rules is:
A) 300 gpd
B) 400 gpd
C) 480 gpd
D) 600 gpd
Answer: C
TCEQ assigns 120 gpd per bedroom; 4 × 120 = 480 gpd.
7. A soil texture feels gritty, doesn’t ribbon, and leaves no stain. It is:
A) Clay
B) Loamy sand
C) Silt loam
D) Peat
Answer: B
Gritty, no ribbon, no stain = sand or loamy sand.
8. During a site eval, you find a seasonal high water table at 14 inches. Which OSSF can be installed?
A) Standard trench
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,B) Shallow trench
C) Mound system
D) Cesspool
Answer: C
Mound system elevates drainfield above seasonal high water table.
9. A dosing tank pump delivers 20 gpm. The dose volume is 100 gallons. How many minutes per dose?
A) 2 min
B) 5 min
C) 10 min
D) 15 min
Answer: B
Time = dose ÷ pump rate = 100 gal ÷ 20 gpm = 5 minutes.
10. A client has heavy clay soil and 12 inches of depth to rock. Which design is best?
A) Gravelless chamber
B) Drip dispersal with pretreatment
C) Conventional pipe-and-gravel
D) Evapotranspiration bed
Answer: B
Drip dispersal with pretreatment works in shallow soil over rock by applying small volumes.
11. TCEQ requires minimum vertical separation from drainfield bottom to limiting layer:
A) 6 inches
B) 12 inches
C) 24 inches
D) 36 inches
Answer: B
12 inches of unsaturated soil required for treatment; 18–24″ for conventional trenches? TCEQ says 12″ min but 24″
for standard trench.
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, 12. A 1500-gallon septic tank receives 480 gpd. What is the detention time?
A) 1.5 days
B) 2.5 days
C) 3.1 days
D) 4.0 days
Answer: C
1500 gal ÷ 480 gpd = 3.125 days ≈ 3.1 days.
13. A repair permit is needed when:
A) Adding a garbage disposal
B) Replacing septic tank lid
C) Effluent surfaces in yard
D) Pumping tank every 5 years
Answer: C
Effluent surfacing indicates failure; requires repair permit.
14. You find a 1000-gallon septic tank for a 3-bedroom house built in 1985. Is it compliant?
A) Yes, if no hydraulic issues
B) No, needs 1500 gallons
C) Only if daily flow <300 gpd
D) Yes if dual-compartment
Answer: B
Current rule: minimum 1500 gal for 3-bedroom; older tanks grandfathered until repair.
15. What is the maximum allowable BOD for Type I effluent?
A) 10 mg/L
B) 30 mg/L
C) 45 mg/L
D) 125 mg/L
Answer: B
Type I = septic tank effluent ≤30 mg/L BOD (after tank, no advanced treatment).
4|Page SUCCESS!!!
QUESTIONS, MATH FORMULAS, & SITE EVALUATION ANSWERS | 100% GUARANTEED
PASS!!!
1. A site has deep, permeable clay loam over fractured bedrock at 18 inches. Which system is prohibited?
A) Low-pressure pipe
B) Evapotranspiration bed
C) Conventional trench with 24″ depth
D) Drip dispersal with pretreatment
Answer: C
Trenches require 24″ of suitable soil below trench bottom; fractured bedrock at 18″ fails separation requirement.
2. During a perc test, water drops 1 inch in 20 minutes. What is the perc rate in minutes per inch?
A) 10 min/in
B) 20 min/in
C) 30 min/in
D) 40 min/in
Answer: B
Perc rate = minutes ÷ inches dropped = 20 min/1 inch = 20 min/in.
3. A site has 40% slope. Which system is NOT allowed without major modification?
A) Spray irrigation
B) Drip dispersal
C) Conventional trench
D) At-grade system
Answer: C
Conventional trenches limited to <15% slope; 40% requires pressure-dosed or drip systems.
4. You measure 12 inches of loamy sand over 6 inches of clay. What is the limiting layer?
A) Loamy sand
B) Clay
1|Page SUCCESS!!!
,C) The interface
D) Groundwater
Answer: B
Clay acts as a limiting layer due to low permeability, regardless of depth.
5. A homeowner wants an OSSF within 50 feet of a stream. What is required?
A) 200% sizing increase
B) Advanced treatment (Type II)
C) No OSSF allowed
D) Only a septic tank
Answer: B
Within 50–100 ft of surface water, Type II treatment (≤10 mg/L BOD/TSS) mandatory.
6. Daily flow for a 4-bedroom house in TCEQ rules is:
A) 300 gpd
B) 400 gpd
C) 480 gpd
D) 600 gpd
Answer: C
TCEQ assigns 120 gpd per bedroom; 4 × 120 = 480 gpd.
7. A soil texture feels gritty, doesn’t ribbon, and leaves no stain. It is:
A) Clay
B) Loamy sand
C) Silt loam
D) Peat
Answer: B
Gritty, no ribbon, no stain = sand or loamy sand.
8. During a site eval, you find a seasonal high water table at 14 inches. Which OSSF can be installed?
A) Standard trench
2|Page SUCCESS!!!
,B) Shallow trench
C) Mound system
D) Cesspool
Answer: C
Mound system elevates drainfield above seasonal high water table.
9. A dosing tank pump delivers 20 gpm. The dose volume is 100 gallons. How many minutes per dose?
A) 2 min
B) 5 min
C) 10 min
D) 15 min
Answer: B
Time = dose ÷ pump rate = 100 gal ÷ 20 gpm = 5 minutes.
10. A client has heavy clay soil and 12 inches of depth to rock. Which design is best?
A) Gravelless chamber
B) Drip dispersal with pretreatment
C) Conventional pipe-and-gravel
D) Evapotranspiration bed
Answer: B
Drip dispersal with pretreatment works in shallow soil over rock by applying small volumes.
11. TCEQ requires minimum vertical separation from drainfield bottom to limiting layer:
A) 6 inches
B) 12 inches
C) 24 inches
D) 36 inches
Answer: B
12 inches of unsaturated soil required for treatment; 18–24″ for conventional trenches? TCEQ says 12″ min but 24″
for standard trench.
3|Page SUCCESS!!!
, 12. A 1500-gallon septic tank receives 480 gpd. What is the detention time?
A) 1.5 days
B) 2.5 days
C) 3.1 days
D) 4.0 days
Answer: C
1500 gal ÷ 480 gpd = 3.125 days ≈ 3.1 days.
13. A repair permit is needed when:
A) Adding a garbage disposal
B) Replacing septic tank lid
C) Effluent surfaces in yard
D) Pumping tank every 5 years
Answer: C
Effluent surfacing indicates failure; requires repair permit.
14. You find a 1000-gallon septic tank for a 3-bedroom house built in 1985. Is it compliant?
A) Yes, if no hydraulic issues
B) No, needs 1500 gallons
C) Only if daily flow <300 gpd
D) Yes if dual-compartment
Answer: B
Current rule: minimum 1500 gal for 3-bedroom; older tanks grandfathered until repair.
15. What is the maximum allowable BOD for Type I effluent?
A) 10 mg/L
B) 30 mg/L
C) 45 mg/L
D) 125 mg/L
Answer: B
Type I = septic tank effluent ≤30 mg/L BOD (after tank, no advanced treatment).
4|Page SUCCESS!!!
