Texas, TCEQ, Wastewater Treatment, Class D
Free Flow and Volume Practice: Texas Class D Wastewater
Last reviewed 2026-08-01. Facts link to their official source.
Free flow and volume practice problems for the Texas Class D wastewater operator exam. You practice the flow triangle: volume, flow rate, and time, solved for whichever one the question hides. Every problem uses fresh numbers, checks your answer, and shows all ten worked steps with nothing skipped. Progress saves on your device.
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One full worked example, every step shown
You practice the flow triangle: volume, flow rate, and time, solved for whichever one the question hides. This example works gallons moved from flow and run time from start to finish. Every number traces to the question, a named conversion, or the line before it.
1. What you know
Pump flow: 250 gpm. Run time: 90 min.
2. What you need
The total gallons moved over the whole run.
3. Match the units
Flow is already per minute and the time is already in minutes, so nothing needs converting before the multiply.
4. Choose the formula
The pump moves the same gallons every minute, so multiplying by the minutes counts the whole delivery.
gallons = gpm x minutes
5. Put in the values
Put each labeled value into the formula before doing any arithmetic.
gal = 250 x 90
6. Track the units
Minutes divide out. Gallons is the unit that remains.
gal/min x min -> gal
7. Work it
One operation, one line.
250 x 90 = 22500
8. Round at the end
The rule here: round to the nearest whole gallon at the end. 22500 becomes 22500 gal.
9. Check the answer
22500 gallons should be far larger than the 250 gallons moved in a single minute, and it is. The unit left is gallons, which is what the question asked for.
10. What it means
This is how you turn a pump reading and a run time into the water actually delivered, such as checking how much a well filled the storage tank overnight.
The formulas in this module
Gallons moved from flow and run time
gallons = gpm x minutes
The pump moves the same gallons every minute, so multiplying by the minutes counts the whole delivery.
Flow rate from gallons and minutes
gpm = gallons / minutes
Flow rate asks what happened in one minute, so divide the total gallons across the minutes it took.
Time to move a volume at a known flow
minutes = gallons / gpm
Each minute removes one flow's worth of gallons, so dividing counts how many minutes the volume takes.
Where this fits in the official exam
- The official subject list this module serves
- Twenty official Need-to-Know subject categories, from Statutes and Rules through Math Problems (incl. Permits, Design Criteria, Safety, Laboratory, Collection, Pumping, treatment stages, Process Control, Disinfection, Sludge Digestion, Biosolids, Effluent Disposal).
- Source: TCEQ Wastewater Operator Exam Knowledge ('What You Need to Know for a Class D Wastewater Treatment Plant Operator Exam' table.)