OSSF DR Test Practice Questions and
Answers | Latest Version | 2025/2026 |
Correct & Verified
What is the primary purpose of an OSSF system?
✔✔To treat and dispose of household wastewater safely on the property.
What agency regulates OSSFs in Texas?
✔✔The Texas Commission on Environmental Quality (TCEQ).
What is the maximum design flow allowed for a standard OSSF permit in Texas?
✔✔5,000 gallons per day.
What is the most common type of OSSF system used in rural Texas?
✔✔Conventional septic tank with a drainfield.
What is the function of a septic tank in an OSSF system?
✔✔To separate solids from wastewater and begin anaerobic digestion.
1
,What is effluent in OSSF terminology?
✔✔Partially treated wastewater discharged from a septic tank or treatment unit.
What is the purpose of a soil absorption system?
✔✔To filter and further treat effluent by percolation through soil.
What type of soil is least suitable for a standard drainfield?
✔✔Clay soil.
What is a percolation test used for in OSSF design?
✔✔To measure how quickly water soaks into soil.
What is the minimum horizontal separation distance from a septic tank to a private water well?
✔✔50 feet.
What is the minimum separation distance from an absorption field to a private water well?
✔✔100 feet.
2
,What is the minimum separation distance from an absorption field to a public water well?
✔✔150 feet.
What is the minimum setback distance from an OSSF to a property line?
✔✔5 feet.
What is the minimum setback distance from an OSSF to a swimming pool?
✔✔5 feet.
What is the minimum separation distance from an absorption field to a stream or pond?
✔✔75 feet.
What is the minimum vertical separation required between the bottom of a drainfield and
groundwater?
✔✔2 feet.
What is the purpose of an aerobic treatment unit (ATU)?
✔✔To provide advanced wastewater treatment using oxygen.
3
, Why might an ATU be required instead of a conventional septic system?
✔✔Because of poor soil conditions or small lot size.
What is the typical chlorine contact time required for ATU disinfection?
✔✔At least 30 minutes.
What is the purpose of an effluent filter in a septic tank?
✔✔To reduce solids entering the drainfield.
What is the minimum tank size required for a single-family residence with up to three bedrooms?
✔✔750 gallons.
What is the minimum tank size required for a four-bedroom house?
✔✔1,000 gallons.
What is the daily wastewater flow estimate used for design per bedroom?
✔✔75 gallons per day per bedroom.
4
Answers | Latest Version | 2025/2026 |
Correct & Verified
What is the primary purpose of an OSSF system?
✔✔To treat and dispose of household wastewater safely on the property.
What agency regulates OSSFs in Texas?
✔✔The Texas Commission on Environmental Quality (TCEQ).
What is the maximum design flow allowed for a standard OSSF permit in Texas?
✔✔5,000 gallons per day.
What is the most common type of OSSF system used in rural Texas?
✔✔Conventional septic tank with a drainfield.
What is the function of a septic tank in an OSSF system?
✔✔To separate solids from wastewater and begin anaerobic digestion.
1
,What is effluent in OSSF terminology?
✔✔Partially treated wastewater discharged from a septic tank or treatment unit.
What is the purpose of a soil absorption system?
✔✔To filter and further treat effluent by percolation through soil.
What type of soil is least suitable for a standard drainfield?
✔✔Clay soil.
What is a percolation test used for in OSSF design?
✔✔To measure how quickly water soaks into soil.
What is the minimum horizontal separation distance from a septic tank to a private water well?
✔✔50 feet.
What is the minimum separation distance from an absorption field to a private water well?
✔✔100 feet.
2
,What is the minimum separation distance from an absorption field to a public water well?
✔✔150 feet.
What is the minimum setback distance from an OSSF to a property line?
✔✔5 feet.
What is the minimum setback distance from an OSSF to a swimming pool?
✔✔5 feet.
What is the minimum separation distance from an absorption field to a stream or pond?
✔✔75 feet.
What is the minimum vertical separation required between the bottom of a drainfield and
groundwater?
✔✔2 feet.
What is the purpose of an aerobic treatment unit (ATU)?
✔✔To provide advanced wastewater treatment using oxygen.
3
, Why might an ATU be required instead of a conventional septic system?
✔✔Because of poor soil conditions or small lot size.
What is the typical chlorine contact time required for ATU disinfection?
✔✔At least 30 minutes.
What is the purpose of an effluent filter in a septic tank?
✔✔To reduce solids entering the drainfield.
What is the minimum tank size required for a single-family residence with up to three bedrooms?
✔✔750 gallons.
What is the minimum tank size required for a four-bedroom house?
✔✔1,000 gallons.
What is the daily wastewater flow estimate used for design per bedroom?
✔✔75 gallons per day per bedroom.
4
