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Water & Wastewater Operator (WPI/ABC Class I) — Practice Exam

WD components: mains: practice questions

Our Water/Wastewater Operator bank has 16 questions on this topic. Here are 4 of them with answers; the full mock exam draws from every topic, like the real one.

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Question 1 · Water Distribution Class I

What usually happens to a pipe's C-factor as old unlined cast iron mains age?

  1. It stays the same
  2. It stays exactly the same
  3. It increases as the pipe walls wear smooth from years of flow
  4. It decreases as tuberculation roughens the pipe
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D. It decreases as tuberculation roughens the pipe — Cleaning and lining can restore capacity.

Question 2 · Water Distribution Class I

Before a new main is placed in service, what must be done?

  1. Paint every hydrant on the new main and fill it with untreated raw water so the joints settle in
  2. Nothing; it can be used immediately
  3. Paint the hydrants and fill the main with untreated raw water to settle it
  4. Pressure and leak test it, disinfect it and get satisfactory bacteriological results
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D. Pressure and leak test it, disinfect it and get satisfactory bacteriological results — AWWA standards cover testing and disinfection.

Question 3 · Water Distribution Class I

How deep must water mains be buried in cold climates?

  1. Only 6 inches
  2. Exactly 2 feet everywhere
  3. Below the frost line
  4. At the surface
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C. Below the frost line — Cover depth depends on local frost penetration.

Question 4 · Water Distribution Class I

What does the Hazen-Williams C-factor describe?

  1. The pipe's pressure rating, in pounds per square inch at the working temperature
  2. The pipe's chlorine demand
  3. The smoothness (carrying capacity) of a pipe's interior
  4. The chlorine demand in the pipe
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C. The smoothness (carrying capacity) of a pipe's interior — Higher C means smoother pipe and less head loss.

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