ONSITE SEWAGE SYSTEM INSTALLER EXAM
2026 EXAMPREP STUDY GUIDE WITH
COMPLETE Q&A
◉ What is the requirement for commercial systems with flow
greater than 500 gallons per day? Answer: A minimum of two
pumps is required, and each pump shall dose alternately.
◉ What is the minimum header size for a typical lift dosed system?
Answer: 4 inches
◉ What distinguishes low pressure dosing systems from gravity and
lift dose systems? Answer: The drain line length is not limited to 100
feet, allowing for more even flow.
◉ What type of material is used for the distribution network in low
pressure dosing systems? Answer: Schedule 40 PVC or equal
material with half-inch or smaller drilled holes.
◉ What happens to the ends of the low pressure dosed lines?
Answer: They are capped and are never looped in a continuous
circuit.
, ◉ What is the total depth required for a subsurface drain field
trench? Answer: 12 inches, including a minimum of six inches of
aggregate below the pipe.
◉ What is the function of the audio-visual high water alarm in a lift-
dose system? Answer: To alert when the water level in the tank is
too high.
◉ What is the role of the pump in a lift-dose system? Answer: To lift
the effluent into the header or distribution box for gravity
distribution.
◉ What is the typical configuration of a subsurface gravity flow
system? Answer: It includes a septic tank and drain lines where
effluent flows by gravity.
◉ What is the purpose of the header pipe in lieu of a distribution
box? Answer: To extend to within 18 inches of the sidewalls.
◉ What is the significance of the biomat in a septic system? Answer:
It can clog the infiltrative surface, leading to localized saturation and
system failure.
◉ What is the minimum aggregate required above a perforated
drain field pipe? Answer: Two inches
2026 EXAMPREP STUDY GUIDE WITH
COMPLETE Q&A
◉ What is the requirement for commercial systems with flow
greater than 500 gallons per day? Answer: A minimum of two
pumps is required, and each pump shall dose alternately.
◉ What is the minimum header size for a typical lift dosed system?
Answer: 4 inches
◉ What distinguishes low pressure dosing systems from gravity and
lift dose systems? Answer: The drain line length is not limited to 100
feet, allowing for more even flow.
◉ What type of material is used for the distribution network in low
pressure dosing systems? Answer: Schedule 40 PVC or equal
material with half-inch or smaller drilled holes.
◉ What happens to the ends of the low pressure dosed lines?
Answer: They are capped and are never looped in a continuous
circuit.
, ◉ What is the total depth required for a subsurface drain field
trench? Answer: 12 inches, including a minimum of six inches of
aggregate below the pipe.
◉ What is the function of the audio-visual high water alarm in a lift-
dose system? Answer: To alert when the water level in the tank is
too high.
◉ What is the role of the pump in a lift-dose system? Answer: To lift
the effluent into the header or distribution box for gravity
distribution.
◉ What is the typical configuration of a subsurface gravity flow
system? Answer: It includes a septic tank and drain lines where
effluent flows by gravity.
◉ What is the purpose of the header pipe in lieu of a distribution
box? Answer: To extend to within 18 inches of the sidewalls.
◉ What is the significance of the biomat in a septic system? Answer:
It can clog the infiltrative surface, leading to localized saturation and
system failure.
◉ What is the minimum aggregate required above a perforated
drain field pipe? Answer: Two inches
