OSSF INSTALLER 1 CORE EXAM MANUAL 2025/2026
QUESTIONS AND ANSWERS GRADED A++
✔✔What is physical straining in relation to soil treatment - ✔✔bacteria are larger than
soil pore opening, increased efficiency
✔✔What is flow rate in relation to soil treatment - ✔✔low flow has better efficiency of
virus removal
✔✔What factors influence bacteria survival in soil - ✔✔moisture, temperature, pH and
organic matter
✔✔What OSSF should be used in clay soil - ✔✔drip or spray irrigation
✔✔Adsorption will occur - ✔✔in water with high hardiness and pH 6.5-7
✔✔Can a septic tank be considered a pretreatment system - ✔✔yes
✔✔A standard disposal system does NOT include - ✔✔gravel less pipes
✔✔A nonstandard disposal system does NOT include - ✔✔drip irrigation
✔✔What should a site evaluation include - ✔✔soil and geologic conditions, lot size,
topography and slope, setbacks /separation distances, flood hazard info
✔✔Soil from largest to smallest - ✔✔gravel (2+mm) sand (.05-2mm) silt (.002-.05mm)
clay (less than .002mm)
✔✔What are the 4 major components of soil - ✔✔organic, air filled, water filled, mineral
✔✔Soil texture - ✔✔the relative proportion of sand, silt and clay in soil
✔✔Porosity - ✔✔the percentage of soil that is occupied by pores or space
✔✔Specific yeild - ✔✔the amount of water drained from soil by gravity
✔✔Specific retention - ✔✔amount of water remaining after gravity drainage
✔✔Permeability - ✔✔the capacity of a material to transmit water
✔✔Uniform grains have high porosity - ✔✔true
✔✔Non uniform grains have low porosity - ✔✔true
, ✔✔Fractured rock has what type of porosity - ✔✔high
✔✔Clay porosity and specific yield - ✔✔45-55% and 1-10
✔✔Gravel porosity and specific yield - ✔✔25-40% and 15-30
✔✔Sand porosity and specific yield - ✔✔25-40% and 10-30
✔✔What are the 3 chemical properties of soil - ✔✔cation exchange capacity, salinity
and pH
✔✔What is the soil horizon - ✔✔a layer lying below another layer and parallel to the
surface
✔✔Top layer soil profile - ✔✔organic layer mixed with minerals
✔✔Middle layer of soil profile - ✔✔weather produced soil with little organic matter
✔✔Bottom layer of soil profile - ✔✔unweathered bedrock
✔✔What is Class 1a soil - ✔✔sandy with 30% or more gravel- unsuitable for drainfield
use
✔✔What is Class 1b soil - ✔✔sandy
✔✔What is class 2 soil - ✔✔coarse loam
✔✔What is class 3 soil - ✔✔fine loam, sandy clay
✔✔What is class 4 soil - ✔✔clay- unsuitable for drainfield use
✔✔Slope unsuitable for drainfield - ✔✔over 30% or complex slopes
✔✔Cannot have unsuitable soil within how many feet of sidewall or bottom of
excavation - ✔✔2 feet (excepted lined ET)
✔✔For suitable construction, how many feet away from restrictive horizon must you be -
✔✔2 feet
✔✔Gravel in soil for drainfield - ✔✔less than 30% if gravel > 2mm or over 80% of gravel
must be < 5mm
✔✔Can you have evidence of groundwater within 2 feet of excavation - ✔✔No
QUESTIONS AND ANSWERS GRADED A++
✔✔What is physical straining in relation to soil treatment - ✔✔bacteria are larger than
soil pore opening, increased efficiency
✔✔What is flow rate in relation to soil treatment - ✔✔low flow has better efficiency of
virus removal
✔✔What factors influence bacteria survival in soil - ✔✔moisture, temperature, pH and
organic matter
✔✔What OSSF should be used in clay soil - ✔✔drip or spray irrigation
✔✔Adsorption will occur - ✔✔in water with high hardiness and pH 6.5-7
✔✔Can a septic tank be considered a pretreatment system - ✔✔yes
✔✔A standard disposal system does NOT include - ✔✔gravel less pipes
✔✔A nonstandard disposal system does NOT include - ✔✔drip irrigation
✔✔What should a site evaluation include - ✔✔soil and geologic conditions, lot size,
topography and slope, setbacks /separation distances, flood hazard info
✔✔Soil from largest to smallest - ✔✔gravel (2+mm) sand (.05-2mm) silt (.002-.05mm)
clay (less than .002mm)
✔✔What are the 4 major components of soil - ✔✔organic, air filled, water filled, mineral
✔✔Soil texture - ✔✔the relative proportion of sand, silt and clay in soil
✔✔Porosity - ✔✔the percentage of soil that is occupied by pores or space
✔✔Specific yeild - ✔✔the amount of water drained from soil by gravity
✔✔Specific retention - ✔✔amount of water remaining after gravity drainage
✔✔Permeability - ✔✔the capacity of a material to transmit water
✔✔Uniform grains have high porosity - ✔✔true
✔✔Non uniform grains have low porosity - ✔✔true
, ✔✔Fractured rock has what type of porosity - ✔✔high
✔✔Clay porosity and specific yield - ✔✔45-55% and 1-10
✔✔Gravel porosity and specific yield - ✔✔25-40% and 15-30
✔✔Sand porosity and specific yield - ✔✔25-40% and 10-30
✔✔What are the 3 chemical properties of soil - ✔✔cation exchange capacity, salinity
and pH
✔✔What is the soil horizon - ✔✔a layer lying below another layer and parallel to the
surface
✔✔Top layer soil profile - ✔✔organic layer mixed with minerals
✔✔Middle layer of soil profile - ✔✔weather produced soil with little organic matter
✔✔Bottom layer of soil profile - ✔✔unweathered bedrock
✔✔What is Class 1a soil - ✔✔sandy with 30% or more gravel- unsuitable for drainfield
use
✔✔What is Class 1b soil - ✔✔sandy
✔✔What is class 2 soil - ✔✔coarse loam
✔✔What is class 3 soil - ✔✔fine loam, sandy clay
✔✔What is class 4 soil - ✔✔clay- unsuitable for drainfield use
✔✔Slope unsuitable for drainfield - ✔✔over 30% or complex slopes
✔✔Cannot have unsuitable soil within how many feet of sidewall or bottom of
excavation - ✔✔2 feet (excepted lined ET)
✔✔For suitable construction, how many feet away from restrictive horizon must you be -
✔✔2 feet
✔✔Gravel in soil for drainfield - ✔✔less than 30% if gravel > 2mm or over 80% of gravel
must be < 5mm
✔✔Can you have evidence of groundwater within 2 feet of excavation - ✔✔No
