Pass your water or wastewater operator exam.
Practice questions for Class/Grade I and II treatment, distribution and collection exams. You see every math step, and a tutor helps with the problems you get wrong. Our code computes each numeric answer and checks the units, so the answer key matches the math.
A rectangular primary clarifier is 100 ft long, 30 ft wide and 12 ft deep. Flow is 2,000,000 gpd. What is the detention time in hours?
- Volume = 100 × 30 × 12 × 7.48 = 269,280 gal
- Flow = 2,000,000 gpd ÷ 24 = 83,333.3 gal/hr
- Detention time = 269,280 ÷ 83,333.3 = 3.23 hours
Answer3.23 hours
Exams passed, Maryland, May 2019
Many operators fail the first time
In May 2019, operators passed 27% of the certification exams Maryland gave that month: 36% of paper wastewater exams and 20% of paper water exams (Maryland Board of Waterworks and Waste Systems Operators minutes). Math is where many people lose points: detention time, chlorine dose, the pounds formula, F/M and MCRT.
Most study apps only tell you that you got a question wrong. Some answer keys contain mistakes or round differently from the exam. You end up searching for the formula on your own.
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One payment. Six months of access to one exam: pick the type (wastewater treatment, water treatment, water distribution or wastewater collection) and the level (Class/Grade I or II). No subscription.
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Access opens by December 15, 2026 for wastewater treatment and water treatment, and by January 31, 2027 for water distribution and wastewater collection. You get a full refund on request any time before your access opens and for 14 days after.
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Does it match my state's exam?
Many states use standardized Class I to IV exams built from published content outlines. Some states, including California and Texas, write their own. Tell us your state when you sign up and we'll tell you how well we cover it before you pay. If we don't cover it, we refund you.
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The one on your application: wastewater treatment, water treatment, water distribution or wastewater collection, at your level. Your pre-order covers one exam. Email us if you need more than one.
What if an answer is wrong?
Flag it with one tap. We review flagged questions within 2 business days and fix or remove them. Our code computes every numeric answer; the AI tutor explains the steps but doesn't produce the answer key.
Is this official?
No. PassOperator is independent. We write our own questions. We don't copy exam questions or other publishers' question banks.
Do you have team pricing?
Yes, for utilities that train several operators. Email passoperator.help@gmail.com.