1|Page
ILLINOIS CLASS D WATER LICENSE TEST 2025/ 2026
NEWEST ACTUAL EXAM CURRENTLY TESTING
COMPLETE EXAM QUESTIONS WITH DETAILED
VERIFIED ANSWERS WITH RATIONALES (100%
CORRECT ANSWERS) /ALREADY GRADED
A+||LATEST EXAM!!
Two Towers are both 125 feet high, when full, contain 122
feet of water. Tower 1 holds 150,000 gallons. Tower 2
holds 500,000 gallons. Each has a pressure gauge at the
base. Which will register the most pressure in psi? -
Answer-Both will be equal
If the water level in tower 1 is 118 feet what will the
pressure reading be at the base - Answer-51.1 psi
What is the definition of potable water - Answer-Water that
does not contain objectable pollution, contamination, or
infective agents and is considered safe for drinking
What is the first item used when installing a service line to
a customer? - Answer-Corporation stop
,2|Page
If a meter to a residence is located in the basement what
should be located between the water main and the house -
Answer-curb stop
A 5/8" x 3/4" water meter serves a residence. Over a
period of years the meter __________ in recording actual
water used - Answer-Decreases
To isolate part of a distribution system what type of valve
is commonly used? - Answer-Gate valve
Trihalomethanes (THMs) are caused by? - Answer-
Reaction of chlorinated water with numeric materials found
in surface water sources
The longer the contact time water and chlorine residuals
enjoy the ________ the THM level will probably be -
Answer-Higher
THM's should be eliminated from finished water because
they cause ? - Answer-Cancer
, 3|Page
The maximum contaminant level for THM's is? - Answer-
.080 mg/l
When collecting THM samples one sample must be taken
at a site where the water has been in the distribution
system the longest time - Answer-True
An applicant for a class d test who has graduated high
school but has no approved training credits must have
____________ "hands on" experience - Answer-6 months
What type of water main is most likely to become
contaminated from gasoline saturated soil - Answer-PVC
What type of materials must not be used as backfill for
water mains? - Answer-Cinders
Nitrate in levels above _________ mg/L can cause "blue
baby" disease - Answer-10
A boil order must be issued if systems pressure drops
below 20 psi or if contaminated of any part of the system
ILLINOIS CLASS D WATER LICENSE TEST 2025/ 2026
NEWEST ACTUAL EXAM CURRENTLY TESTING
COMPLETE EXAM QUESTIONS WITH DETAILED
VERIFIED ANSWERS WITH RATIONALES (100%
CORRECT ANSWERS) /ALREADY GRADED
A+||LATEST EXAM!!
Two Towers are both 125 feet high, when full, contain 122
feet of water. Tower 1 holds 150,000 gallons. Tower 2
holds 500,000 gallons. Each has a pressure gauge at the
base. Which will register the most pressure in psi? -
Answer-Both will be equal
If the water level in tower 1 is 118 feet what will the
pressure reading be at the base - Answer-51.1 psi
What is the definition of potable water - Answer-Water that
does not contain objectable pollution, contamination, or
infective agents and is considered safe for drinking
What is the first item used when installing a service line to
a customer? - Answer-Corporation stop
,2|Page
If a meter to a residence is located in the basement what
should be located between the water main and the house -
Answer-curb stop
A 5/8" x 3/4" water meter serves a residence. Over a
period of years the meter __________ in recording actual
water used - Answer-Decreases
To isolate part of a distribution system what type of valve
is commonly used? - Answer-Gate valve
Trihalomethanes (THMs) are caused by? - Answer-
Reaction of chlorinated water with numeric materials found
in surface water sources
The longer the contact time water and chlorine residuals
enjoy the ________ the THM level will probably be -
Answer-Higher
THM's should be eliminated from finished water because
they cause ? - Answer-Cancer
, 3|Page
The maximum contaminant level for THM's is? - Answer-
.080 mg/l
When collecting THM samples one sample must be taken
at a site where the water has been in the distribution
system the longest time - Answer-True
An applicant for a class d test who has graduated high
school but has no approved training credits must have
____________ "hands on" experience - Answer-6 months
What type of water main is most likely to become
contaminated from gasoline saturated soil - Answer-PVC
What type of materials must not be used as backfill for
water mains? - Answer-Cinders
Nitrate in levels above _________ mg/L can cause "blue
baby" disease - Answer-10
A boil order must be issued if systems pressure drops
below 20 psi or if contaminated of any part of the system
