Level 1 Water Distribution Exam Prep (50 Questions)
1. What is the primary purpose of a water distribution system?
To deliver safe, adequate, and reliable water to consumers.
2. What does PSI stand for in water distribution?
Pounds per square inch (a unit of pressure).
3. What is the minimum pressure recommended in a distribution system under normal conditions?
20 psi (Ontario guidelines require maintaining minimum pressure).
4. What is the most common material used for water service lines today?
High-density polyethylene (HDPE) or copper.
5. What is the purpose of a backflow prevention device?
To prevent contamination of the potable water system due to backflow or back-siphonage.
6. What does SCADA stand for?
Supervisory Control and Data Acquisition.
7. What type of valve is typically used to isolate sections of a distribution system?
Gate valve.
8. What type of valve is used to regulate flow and pressure?
Globe valve or pressure reducing valve (PRV).
9. What is the main purpose of a hydrant in a distribution system?
Fire protection, flushing mains, and sometimes sampling.
10. What is unidirectional flushing?
A method of flushing water mains by closing valves and opening hydrants in a sequence to achieve high velocity and remove sediment.
11. What is water hammer?
A surge of pressure caused by sudden changes in flow velocity, such as quick valve closure.
12. What is the main purpose of an air release valve?
To remove trapped air from the water main and prevent blockages.
13. What is the minimum chlorine residual required in a distribution system in Ontario?
0.05 mg/L free chlorine residual.
14. What is the purpose of looping water mains instead of dead ends?
To improve circulation, reduce stagnant water, and maintain chlorine residuals.
15. What does GPM stand for?
Gallons per minute (a flow measurement).
16. What is the recommended minimum separation distance between water mains and sanitary sewers?
Typically 3 meters horizontally, and water mains should be placed above sewers.
17. What type of drawing shows the layout of water mains, valves, and hydrants?
A distribution system map or record drawing.
18. What is the function of a water storage reservoir?
To provide equalization, emergency supply, and fire protection storage.
19. What does cross-connection mean?
A physical link between potable water and a possible source of contamination.
20. What is the most common cause of low pressure in a distribution system?
High demand, leaks, or pump/valve malfunction.
21. What does SCBA stand for?
Self-Contained Breathing Apparatus (used for confined space entry).
22. What is a confined space in water distribution work?
An enclosed or partially enclosed space with limited entry/exit and potential hazardous atmosphere (e.g., valve chamber).
23. What is the main health concern with lead service lines?
Lead leaching into drinking water, causing health risks especially to children and pregnant women.
24. What is the purpose of cathodic protection?
To prevent corrosion of metallic water mains and tanks.
25. What does NRW stand for?
Non-Revenue Water (water produced but not billed, due to leaks, theft, or metering issues).
26. What is the recommended flushing velocity for cleaning water mains?
At least 2.5 ft/s.
27. What is the function of a pressure reducing valve (PRV)?
To lower and regulate pressure in a distribution zone.
28. What is the function of a booster pumping station?
To increase pressure and flow to higher elevation zones.
29. What is the main risk of back-siphonage?
Contaminants entering the potable water system when system pressure drops.
30. What type of hydrant is most commonly used in Canada?
Dry barrel hydrant (suitable for freezing climates).
31. What does a distribution operator use a leak detector for?
To locate underground leaks by detecting sound or vibrations.
32. What is the function of a flow meter in a distribution system?
To measure water consumption, flow rates, and detect leakage.
33. What does SOP stand for?
Standard Operating Procedure.
34. What is the safe minimum oxygen level in a confined space?
19.5% oxygen.
35. What type of test is commonly used to measure chlorine residual?
DPD colorimetric test.
36. What is the typical lifespan of a water main?
50–100 years, depending on material and conditions.
37. What is the main reason for unaccounted-for water?
Leaks, inaccurate meters, theft, or flushing.
38. What does psi measure?
Pressure of water in the distribution system.
39. What does an operator use a valve exercising program for?
To ensure valves operate properly and don’t seize up.
40. What is the purpose of water main swabbing?
To clean distribution pipes by forcing a foam swab through them.
41. What is the most common cause of discoloured water in a distribution system?
Iron or manganese sediment stirred up by flow changes.
42. What is the purpose of system mapping and GIS?
To document locations of mains, hydrants, valves, and aid in system management.
43. What is the function of a standpipe or elevated tank?
To provide pressure through elevation and storage capacity.
44. What is the main function of a cross-connection control program?
To prevent contamination of the drinking water system.
45. What is the recommended hydrant spacing in residential areas?
Approximately 150 m (varies by local code).
46. What is the normal operating range of pressure in a distribution system?
Typically 40–100 psi.
47. What is the main purpose of a service connection curb stop?
To allow shutoff of water supply to a building.
48. What does an operator check during a hydrant inspection?
Leaks, operation, lubrication, flow, and accessibility.
49. What is the purpose of a main break repair procedure?
To restore service, disinfect the repaired section, and protect public health.
50. What should an operator always do after repairing a water main?
Flush and disinfect the main, then take bacteriological samples.
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