California D2 Water Distribution Practice Test

Original D2 questions written to the State Water Board’s Expected Range of Knowledge, every option explained.

Free sample · Question 1 of 5Safety

Before entering a permit-required confined space, what must be tested, in this order?

A.Oxygen, then flammable gases, then toxic gasesB.Only carbon monoxideC.Toxic gases, then temperature, then oxygen, then noise levelD.No test is needed if the space smells normal

317 original California D2 questions with explanations · 100-question practice exam · 6 parts

California D2 exam format

California certifies drinking water distribution operators at grades D1 to D5. The D2 exam has 100 questions in six content categories, with counts set for each grade in the Board's Expected Range of Knowledge, taken on computer at Prometric test centers year-round.

Questions: 100: Disinfection 20, Design/Hydraulics 20, Equipment/Maintenance/Inspections 20, Regulations/Management/Safety 10, Mains and Piping 20, Water Quality/Source 10
Where: Computer-based at Prometric test centers in California, year-round
Exam fee: $81; re-exam $56 (fee schedule effective 8/31/2026)
Time and passing score: The Board does not publish the time limit or the passing score for the D exams
Results: Drinking water results are available right after the exam
Recent pass rate: 68% of 981 examinees, January to June 2026 (State Water Board)
To take the exam: A high school diploma or GED and one 36-hour (or 3.6 CEU or 3-semester-unit) course in water supply principles
Certificate: Pass within three years before applying. Certificates are valid three years; renewal needs 16 contact hours

Line drawing of a street cutaway with a buried water main, a gate valve and valve box, a fire hydrant, a service line to a meter box, and an elevated tank behind the houses

What’s on the California D2 exam

The content areas and question counts below are the exam owner’s. Our practice exam uses the same counts; each row links to the free topic drills that practice it.

Content area	What it covers	Questions (official)	Drill
Disinfection	Main, well and reservoir disinfection, chlorine chemistry, chloramination and byproducts	20	Disinfection drill
Distribution System Design / Hydraulics	Layout, storage, demand, pressure, head loss, water hammer, cavitation, cross-connections and backflow	20	Hydraulics drill Backflow drill
Equipment Operation / Maintenance / Inspections	Valves, hydrants, meters, pumps and motors, feeders, generators, SCADA and inspections	20	Mains and valves drill Pumps and equipment drill
Drinking Water Regulations / Management / Safety	SDWA rules, MCLs, sampling, public notice, planning, budgets, safety and emergency response	10	Regulations drill Management drill Safety drill
Water Mains and Piping	Pipe materials, installation, services, repairs, flushing and corrosion	20	Mains and valves drill
Water Quality / Water Source	Sampling and lab results, source water and wells	10	Water lab drill Source water drill

California D2 practice exam100 questions in 180 minutes with a score for every area.Free mixed drill: every areaTen untimed California D2 questions from across the outline, with an explanation after each answer.

How to take the California D2 exam

Check the D2 requirements and apply to the State Water Board with the exam fee ($81).
Once approved, schedule the exam with Prometric at a California test center.
Sit the 100-question exam with the on-screen calculator, scratch paper and the Board’s formula sheet.
Apply for the D2 certificate within three years of passing.

Common questions

How many questions are on the California D2 exam?

100, in six categories: Disinfection 20, Distribution System Design/Hydraulics 20, Equipment Operation/Maintenance/Inspections 20, Drinking Water Regulations/Management/Safety 10, Water Mains and Piping 20 and Water Quality/Water Source 10.

What is the passing score for the D2 exam?

The State Water Board does not publish a passing score or time limit for the distribution exams. Our practice exam reports your score in each category.

What is the D2 pass rate?

68% of 981 examinees passed D2 from January to June 2026, according to the Board's published results.

What do I need to take the D2 exam?

A high school diploma or GED and one 36-hour (or 3.6 CEU or 3-semester-unit) course in water supply principles.

Are these the real exam questions?

No. The Board keeps exam questions confidential. These are original questions written to its published Expected Range of Knowledge, with an explanation for every option.

Ready for exam day?

Take the California D2 practice exam

100 questions in the official content counts, with a score for every area and an explanation for every option.

Or start with a free ten-question drill

More California exam practice

One water operator pass covers every practice exam on the site.

Exam format, content counts, fees and pass rates checked November 2026 on waterboards.ca.gov: State Water Board: Drinking Water Treatment and Distribution Operators · Expected Range of Knowledge, Drinking Water Distribution Exam (rev. 4/2020, PDF) · Drinking Water Operator Certification fee schedule (effective 8/31/2026, PDF) · Distribution operator minimum qualifications (rev. 11/2024, PDF) · Water Distribution exam results (PDF) · Operator Certification Computer-Based Testing FAQs (rev. 2/2023, PDF) · Distribution and Water Treatment Operator Certification Guidance (rev. 6/2024, PDF).

Game Assessment Prep is an independent practice site, not affiliated with or endorsed by Water Professionals International (WPI, formerly ABC), the California State Water Resources Control Board or the Texas Commission on Environmental Quality. Every question is original; none is taken from a certification exam, an official study guide or another prep provider.