Ultimate New Jersey T1 Water Treatment Operator
Exam Study Guide: 100 Comprehensive Practice
Questions, Answers, and Explanations for the 2026
NJDEP Licensing Test
Water Math & Conversions
1. What is the weight of one gallon of water?
o A) 7.48 lbs
o B) 8.34 lbs
o C) 62.4 lbs
o D) 4.33 lbs
o Explanation One gallon of pure water weighs exactly 8.34 pounds at
standard temperature and pressure.
2. How many gallons are in one cubic foot of space?
o A) 7.48 gallons
o B) 8.34 gallons
o C) 3.14 gallons
o D) 27 gallons
o Explanation A volume of one cubic foot can hold exactly 7.48 gallons of
liquid water.
3. Convert a flow rate of 1.5 MGD into gallons per minute (gpm).
o A) 62,500 gpm
o B) 1,041 gpm
o C) 10,416 gpm
o D) 150 gpm
o Explanation Multiply 1.5 by 1,000,000 to get 1,500,000 gallons per day, then
divide by 1,440 minutes in a day.
,4. How many feet of head are created by a 100-foot tall water tank?
o A) 43.3 feet
o B) 100.0 feet
o C) 231.0 feet
o D) 7.48 feet
o Explanation Feet of head represents the vertical height of a water column,
which equals the structural height.
5. Convert a water pressure reading of 45 psi into feet of head.
o A) 19.5 feet
o B) 104 feet
o C) 54 feet
o D) 94 feet
o Explanation Every 1 psi of pressure is equal to 2.31 feet of water column
head (45 x 2.31 = 103.95).
6. Find the volume in gallons of a rectangular basin that is 10ft long, 10ft wide,
and 10ft deep.
o A) 1,000 gallons
o B) 7,480 gallons
o C) 8,340 gallons
o D) 1,440 gallons
o Explanation Multiply length by width by depth to get 1,000 cubic feet, then
multiply by 7.48 gallons per cubic foot.
7. What is the area of a circular tank surface with a 20-foot diameter?
o A) 62.8 sq ft
o B) 314 sq ft
o C) 1,256 sq ft
o D) 400 sq ft
, o Explanation The area of a circle equals 0.785 multiplied by the diameter
squared (0.785 x 20 x 20 = 314).
8. If a plant treats 1 MGD, what is the detention time of a 100,000-gallon tank?
o A) 1.2 hours
o B) 2.4 hours
o C) 4.8 hours
o D) 10 hours
o Explanation Tank volume divided by daily flow equals 0.1 days. Multiply 0.1
days by 24 hours to get 2.4 hours.
9. How many pounds of chlorine gas are needed to dose a 1.0 MGD flow at 3.0
mg/L?
o A) 3.0 lbs/day
o B) 8.34 lbs/day
o C) 25.0 lbs/day
o D) 30.0 lbs/day
o Explanation Using the pounds formula: 1.0 MGD x 3.0 mg/L x 8.34 lbs/gal
equals 25.02 pounds per day.
10. A tank holds 50,000 gallons. How many pounds of chemical are needed for a 2
mg/L dose?
o A) 0.16 lbs
o B) 0.83 lbs
o C) 8.34 lbs
o D) 2.08 lbs
o Explanation Convert 50,000 gallons to 0.05 MGD. Use the pounds formula:
0.05 MGD x 2 mg/L x 8.34 = 0.834 lbs.
Disinfection & Chlorination
11. Which chlorine form is the most powerful disinfectant in water?
Exam Study Guide: 100 Comprehensive Practice
Questions, Answers, and Explanations for the 2026
NJDEP Licensing Test
Water Math & Conversions
1. What is the weight of one gallon of water?
o A) 7.48 lbs
o B) 8.34 lbs
o C) 62.4 lbs
o D) 4.33 lbs
o Explanation One gallon of pure water weighs exactly 8.34 pounds at
standard temperature and pressure.
2. How many gallons are in one cubic foot of space?
o A) 7.48 gallons
o B) 8.34 gallons
o C) 3.14 gallons
o D) 27 gallons
o Explanation A volume of one cubic foot can hold exactly 7.48 gallons of
liquid water.
3. Convert a flow rate of 1.5 MGD into gallons per minute (gpm).
o A) 62,500 gpm
o B) 1,041 gpm
o C) 10,416 gpm
o D) 150 gpm
o Explanation Multiply 1.5 by 1,000,000 to get 1,500,000 gallons per day, then
divide by 1,440 minutes in a day.
,4. How many feet of head are created by a 100-foot tall water tank?
o A) 43.3 feet
o B) 100.0 feet
o C) 231.0 feet
o D) 7.48 feet
o Explanation Feet of head represents the vertical height of a water column,
which equals the structural height.
5. Convert a water pressure reading of 45 psi into feet of head.
o A) 19.5 feet
o B) 104 feet
o C) 54 feet
o D) 94 feet
o Explanation Every 1 psi of pressure is equal to 2.31 feet of water column
head (45 x 2.31 = 103.95).
6. Find the volume in gallons of a rectangular basin that is 10ft long, 10ft wide,
and 10ft deep.
o A) 1,000 gallons
o B) 7,480 gallons
o C) 8,340 gallons
o D) 1,440 gallons
o Explanation Multiply length by width by depth to get 1,000 cubic feet, then
multiply by 7.48 gallons per cubic foot.
7. What is the area of a circular tank surface with a 20-foot diameter?
o A) 62.8 sq ft
o B) 314 sq ft
o C) 1,256 sq ft
o D) 400 sq ft
, o Explanation The area of a circle equals 0.785 multiplied by the diameter
squared (0.785 x 20 x 20 = 314).
8. If a plant treats 1 MGD, what is the detention time of a 100,000-gallon tank?
o A) 1.2 hours
o B) 2.4 hours
o C) 4.8 hours
o D) 10 hours
o Explanation Tank volume divided by daily flow equals 0.1 days. Multiply 0.1
days by 24 hours to get 2.4 hours.
9. How many pounds of chlorine gas are needed to dose a 1.0 MGD flow at 3.0
mg/L?
o A) 3.0 lbs/day
o B) 8.34 lbs/day
o C) 25.0 lbs/day
o D) 30.0 lbs/day
o Explanation Using the pounds formula: 1.0 MGD x 3.0 mg/L x 8.34 lbs/gal
equals 25.02 pounds per day.
10. A tank holds 50,000 gallons. How many pounds of chemical are needed for a 2
mg/L dose?
o A) 0.16 lbs
o B) 0.83 lbs
o C) 8.34 lbs
o D) 2.08 lbs
o Explanation Convert 50,000 gallons to 0.05 MGD. Use the pounds formula:
0.05 MGD x 2 mg/L x 8.34 = 0.834 lbs.
Disinfection & Chlorination
11. Which chlorine form is the most powerful disinfectant in water?
