Nearly half the exam (45 questions) is regulations, management and safety.
For the operators who keep treated water moving through the pipes, pumps, valves and storage between the plant and the customer.
Start studying D5| Content area | % of the exam | |
|---|---|---|
| Disinfection | 10 | |
| Distribution System Design / Hydraulics | 10 | |
| Equipment Operation / Maintenance / Inspections | 15 | |
| Regulations / Management / Safety | 45 | |
| Water Mains and Piping | 5 | |
| Water Quality / Water Source | 15 |
55% of examinees passed (96 of 175) from July 1, 2025 to June 30, 2026. Source: SWRCB Drinking Water Operator Certification Program, Water Distribution Exam Results (through 6/30/2026). The agency updates these tables every six months.
Management: water loss audit · an original practice item written only from publicly available sources, not a real exam question
In a year a system puts 1,200 million gallons (MG) into supply. Billed authorized consumption is 1,020 MG and unbilled authorized use (flushing, firefighting) is 30 MG. Using the American Water Works Association (AWWA) water balance, what are the water losses, and what does that volume work out to as a percentage of system input?
B. 150 MG, 12.5% of system input
Water losses = system input − authorized consumption, and authorized consumption includes both billed and unbilled uses: 1,200 − (1,020 + 30) = 150 MG, which works out to 150 ÷ 1,200 = 12.5% of system input. That percentage is only a calculation, not an AWWA performance indicator: AWWA recommends volume-based indicators, such as gallons per service connection per day and the Infrastructure Leakage Index (ILI), because a percentage shifts with how much water customers use. 180 MG leaves out the unbilled authorized use; 14.3% has the right volume but divides it by authorized consumption (1,050 MG) and labels the result a share of system input; 30 MG is the unbilled authorized use itself, which is consumption, not loss.
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Topic coverage follows Expected Range of Knowledge for Drinking Water Distribution Exam (SWRCB Division of Drinking Water, rev. 4/2020). Practice questions are written only from publicly available sources (that outline and the regulations and references it cites); they are not real exam questions, which are confidential. Check current application requirements, fees and exam dates on the certifying body's own page: official certification page.
Questions, flashcards, and explanations are AI-written from publicly available sources only: the exam content outlines and candidate materials each certifying body publishes without restriction, and the regulations and technical references they cite. No confidential material is used, including actual exam questions, recollections of any exam sat by the author, or any handbook or document released under a confidentiality agreement. Content is then put through repeated review — regulatory values checked against primary sources, every calculation recomputed, and errors corrected — plus spot checks by the author, who holds California water operator certifications and a California civil engineering licence. Those spot checks are sampling, not a professional review: nothing here is stamped, sealed, or offered as engineering advice, and not every item has been individually verified, so mistakes can still slip through.