IL SEPTIC INSTALLERS EXAMINATION
QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS 100%
CORRECT RATED A+ NEWLY UPDATED
2026
Public Sewer Connection – Answer ✔✔
A private residence must connect to a public sewer system if it is within 300 feet of
the property. Commercial buildings with wastewater flow under 1,500 gallons per
day must also connect if located within 300 feet. Commercial properties producing
1,500 gallons per day or more must connect if the sewer is within 1,000 feet.
Exceptions may apply if there is a physical barrier, local ordinance restriction, or if
connection cannot be completed with an individual 4-inch service line. In those
cases, a PSD system may be allowed.
Acceptable Pipe Materials – Answer ✔✔
Approved pipe materials include vitrified clay, ductile iron, and plastic piping.
Any piping located after the septic tank or distribution box must be either vitrified
clay or plastic.
Schedule 40 or Greater – Answer ✔✔
Pipe rated as Schedule 40 or higher is required beneath roads, driveways, and
parking areas.
Gravity Slope – Answer ✔✔
For a 4-inch pipe, the minimum required slope is 12 inches for every 100 feet of
pipe length
Building sewers in excess of 50' should have what? -ANSWER ✔✔A C/O @ least
every 50' from building to tank, distribution box, or ATU
,Creviced Limestone Formation -ANSWER ✔✔SS system cannot be installed
where bottom of system is less than 4' from top of limestone
If limestone is known to be present a soil test must be done @ least 4' deeper than
where the bottom of the trench will be
How far away can quick disconnect be? -ANSWER ✔✔no more than 50' away
from the device & w/in sight of
Experimental Use Permits -ANSWER ✔✔min. of 10 experimental systems
installed b4 unconditional approval granted. Permit valid for 2 yrs & evaluated @
end of 2 yrs.
2 options for garbage grinders -ANSWER ✔✔1. solids retention tank btwn WW
source & septic tk. for kitchen waste only. Needs to be 50% of the size of the
designed septic tank w/ a min. of 500 gals.
2. A septic tank receiving all flows sized as 50% of the septic tank size + septic
tank size. i.e., septic tk = 1500 gals. /2 = 750 + 1500 = 2250 (would need 2500 gal
tk)
How long should a homeowner keep maint. records for their system? -ANSWER
✔✔the life of the system
When should the 1st maintenance of a septic tank after installation be completed
for a residence? -ANSWER ✔✔Prior to or within 3 yrs. After initial inspection it
can be done once every 5 yrs. Can be done by everyone + homeowner
, If sludge layer /suspended solids are greater than 33% . . . -ANSWER ✔✔Must
pump tank and perform maintenance
When should a septic system be evaluated initially after installation for a non-
residential bldg? -ANSWER ✔✔prior to or w/in 3 yrs. After that it should be done
@ least every 3 yrs.
Owner cannot do. has to be engineer, env. health practitioner, member of dept, HD,
or septic contractor
Aerobic Treatment Unit Evaluations -ANSWER ✔✔1 every 6 mos @ least (same
ppl) + HOMEOWNER as long as they follow manufacturer's requirements &
proper maintenance
What is the maint. schedule for SFs & WSPs w/ surface discharges? -ANSWER
✔✔@ least 1 per yr. + H.O. if rules r followed. Pumped when solids & scum
greater than 33%
Can a H.O. install & maintain a septic system on his/her property? -ANSWER
✔✔Yes
Who can perform the excavation for a septic system? -ANSWER ✔✔A licensed
installer (employee while supervised) or the property owner.
What is the min. size tank for flows UP TO 500 gpd? -ANSWER ✔✔750 gals.
If flows are greater than 500 gpd, how do you size the tank? -ANSWER ✔✔Tank
size should be = to @ least 1.5x the estimated sewage flow
QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS 100%
CORRECT RATED A+ NEWLY UPDATED
2026
Public Sewer Connection – Answer ✔✔
A private residence must connect to a public sewer system if it is within 300 feet of
the property. Commercial buildings with wastewater flow under 1,500 gallons per
day must also connect if located within 300 feet. Commercial properties producing
1,500 gallons per day or more must connect if the sewer is within 1,000 feet.
Exceptions may apply if there is a physical barrier, local ordinance restriction, or if
connection cannot be completed with an individual 4-inch service line. In those
cases, a PSD system may be allowed.
Acceptable Pipe Materials – Answer ✔✔
Approved pipe materials include vitrified clay, ductile iron, and plastic piping.
Any piping located after the septic tank or distribution box must be either vitrified
clay or plastic.
Schedule 40 or Greater – Answer ✔✔
Pipe rated as Schedule 40 or higher is required beneath roads, driveways, and
parking areas.
Gravity Slope – Answer ✔✔
For a 4-inch pipe, the minimum required slope is 12 inches for every 100 feet of
pipe length
Building sewers in excess of 50' should have what? -ANSWER ✔✔A C/O @ least
every 50' from building to tank, distribution box, or ATU
,Creviced Limestone Formation -ANSWER ✔✔SS system cannot be installed
where bottom of system is less than 4' from top of limestone
If limestone is known to be present a soil test must be done @ least 4' deeper than
where the bottom of the trench will be
How far away can quick disconnect be? -ANSWER ✔✔no more than 50' away
from the device & w/in sight of
Experimental Use Permits -ANSWER ✔✔min. of 10 experimental systems
installed b4 unconditional approval granted. Permit valid for 2 yrs & evaluated @
end of 2 yrs.
2 options for garbage grinders -ANSWER ✔✔1. solids retention tank btwn WW
source & septic tk. for kitchen waste only. Needs to be 50% of the size of the
designed septic tank w/ a min. of 500 gals.
2. A septic tank receiving all flows sized as 50% of the septic tank size + septic
tank size. i.e., septic tk = 1500 gals. /2 = 750 + 1500 = 2250 (would need 2500 gal
tk)
How long should a homeowner keep maint. records for their system? -ANSWER
✔✔the life of the system
When should the 1st maintenance of a septic tank after installation be completed
for a residence? -ANSWER ✔✔Prior to or within 3 yrs. After initial inspection it
can be done once every 5 yrs. Can be done by everyone + homeowner
, If sludge layer /suspended solids are greater than 33% . . . -ANSWER ✔✔Must
pump tank and perform maintenance
When should a septic system be evaluated initially after installation for a non-
residential bldg? -ANSWER ✔✔prior to or w/in 3 yrs. After that it should be done
@ least every 3 yrs.
Owner cannot do. has to be engineer, env. health practitioner, member of dept, HD,
or septic contractor
Aerobic Treatment Unit Evaluations -ANSWER ✔✔1 every 6 mos @ least (same
ppl) + HOMEOWNER as long as they follow manufacturer's requirements &
proper maintenance
What is the maint. schedule for SFs & WSPs w/ surface discharges? -ANSWER
✔✔@ least 1 per yr. + H.O. if rules r followed. Pumped when solids & scum
greater than 33%
Can a H.O. install & maintain a septic system on his/her property? -ANSWER
✔✔Yes
Who can perform the excavation for a septic system? -ANSWER ✔✔A licensed
installer (employee while supervised) or the property owner.
What is the min. size tank for flows UP TO 500 gpd? -ANSWER ✔✔750 gals.
If flows are greater than 500 gpd, how do you size the tank? -ANSWER ✔✔Tank
size should be = to @ least 1.5x the estimated sewage flow
