Water operator practice problems, solved step by step
Free operator math practice you actually work, not just read. Try each problem on paper, then watch it solved one small step at a time, with a plain-words explanation under every step. Built for the Texas Class D water and wastewater exams, for people who have been out of school a while.
Practice that holds your hand
Watch it first
See the whole problem written out slowly, so you know what a good answer looks like before you try.
Then do it yourself
Work it on paper, then check yourself against the walkthrough step by step.
Never go blank
Every step has a plain-words explanation and a quick trick, so nobody skips ahead and loses you.
Every practice problem
Tap any problem to try it, then watch it solved.
- Water & wastewaterHow much pressure does 92 feet of water make?Try it, then watch
- Water & wastewaterHow many gallons are in a 20 by 10 by 8 foot tank?Try it, then watch
- WaterHow many gallons are in a 30 foot round tank?Try it, then watch
- Water & wastewaterHow many pounds of chlorine for 2 MGD at 3 mg/L?Try it, then watch
- Water & wastewaterHow do you turn 350 GPM into gallons per day?Try it, then watch
- WastewaterWhat is the detention time of a 30,000 gallon tank?Try it, then watch
- WastewaterWhat percent of the BOD was removed?Try it, then watch
- Water & wastewaterWhat is the area of a 40 by 12 foot clarifier?Try it, then watch
- Water & wastewaterWhat is the flow if 6,000 gallons fill in 30 minutes?Try it, then watch
- Water & wastewaterHow many GPM is 1.44 MGD?Try it, then watch
- Water & wastewaterHow much does 500 gallons of water weigh?Try it, then watch
- Water & wastewaterHow many gallons are in 2,000 cubic feet?Try it, then watch
- Water & wastewaterWhat is the detention time in minutes for 5,000 gallons at 250 GPM?Try it, then watch
- Water & wastewaterHow many feet of head is 50 psi?Try it, then watch
- Water & wastewaterWhat percent of capacity is 400 GPM out of 500?Try it, then watch
- WaterHow many gallons are in a 12 foot round tank, 10 feet deep?Try it, then watch
- Water & wastewaterWhat is the area of a 20 foot round clarifier?Try it, then watch
- Water & wastewaterWhat is the area of a 30 by 15 foot basin?Try it, then watch
- Water & wastewaterHow many pounds of chlorine for 0.5 MGD at 2 mg/L?Try it, then watch
- WastewaterWhat is the detention time of a 100,000 gallon tank at 25,000 GPH?Try it, then watch
- WastewaterWhat percent of the TSS was removed, 240 to 60?Try it, then watch
- Water & wastewaterHow much pressure is at the bottom of a 40 foot tank?Try it, then watch
- Water & wastewaterHow do you turn 720,000 GPD into MGD?Try it, then watch
- WaterHow many gallons are in 1,000 feet of 6 inch main?Try it, then watch
- WaterHow many gallons are in 800 feet of 12 inch main?Try it, then watch
- Water & wastewaterWhat is the area of a 25 foot round tank?Try it, then watch
- Water & wastewaterWhat is the area of a 50 by 20 foot basin?Try it, then watch
- WaterHow many pounds of alum for 3 MGD at 12 mg/L?Try it, then watch
- Water & wastewaterHow many GPD is 1,000 GPM?Try it, then watch
- Water & wastewaterWhat is the flow if 12,000 gallons fill in 40 minutes?Try it, then watch
- Water & wastewaterWhat is the detention time for 60,000 gallons at 500 GPM?Try it, then watch
- WastewaterWhat percent of the BOD was removed, 180 to 36?Try it, then watch
- Water & wastewaterHow much pressure does 150 feet of water make?Try it, then watch
- WaterHow many pounds of chlorine to disinfect a 12,000 gallon main?Try it, then watch
- WaterHow many gallons are in 500 feet of 24 inch main?Try it, then watch
- WaterHow many gallons are in 2,000 feet of 8 inch main?Try it, then watch
- WaterWhat percent of the water is lost if 500,000 is pumped and 450,000 delivered?Try it, then watch
More free ways to practice
Water operator math, solved simply
The method behind each formula: volume, dosage, flow, and detention, worked the simplest way.
Operator formula reference
Every Class D formula and constant (7.48, 8.34, 0.785, 0.433) in one printable sheet.
Free operator calculators
Plug in your own numbers for tank volume, chlorine dose, flow, and pump run time.
Free practice tests
Ready to test yourself? Take a full practice run when you have the method down.
Common questions
- Are these real water operator exam questions?
- No. Every problem here is original teaching material, written to practice the same math the exam uses. We never copy real exam questions, and no result here predicts your official score.
- Are the practice problems free?
- Yes. Every worked problem on this page is free to try, with the full step-by-step walkthrough and explanation.
- What math is on the Texas Class D water operator exam?
- Class D covers conversions, area and volume, chemical dosage, flow, and basic detention time. It is closed-book, but you are given a formula and conversion sheet, so the skill is knowing when to use each formula.
- How should I practice operator math if I forgot the basics?
- Watch each problem solved slowly first, then try it yourself on the notebook without looking back. Repeat a few problems a day. Seeing every step, with no gaps, is what makes it stick.
Preparing for the whole exam?
The full Texas Class D prep, when you are ready
These worked problems are free. When you want the full picture, the reviewed question bank covers every Class D subject, with a guided study path, drills, and a timed practice exam.
- Reviewed questions for every Class D subject
- A guided study path that tells you what to do next
- A timed practice exam that mirrors the real format
- Operator math worked step by step, with calculators
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