California certification
D1 — Water Distribution, Grade 1
D1 is California's entry-level water distribution operator certificate. It covers the day-to-day knowledge an operator needs to run, maintain and protect a distribution system: disinfection, hydraulics, mains and piping, equipment, water quality, and the regulations and safety rules that go with the job.
The D1 exam at a glance
100
multiple-choice questions
70%
needed to pass
~63%
2025 California pass rate
$62
current state exam fee
Pass rate from California's official published 2025 results. Check the current fee with the state before you register.
Topic breakdown
How much of the real D1 exam each topic carries, and how many original practice questions we provide for it.
| Topic | Share of exam | Practice Qs |
|---|---|---|
| Disinfection | 15% | 45 |
| Distribution System Design / Hydraulics | 20% | 60 |
| Equipment Operation / Maintenance / Inspections | 20% | 60 |
| Drinking Water Regulations / Management / Safety | 15% | 45 |
| Water Mains and Piping | 20% | 60 |
| Water Quality / Water Source | 10% | 30 |
| Total | 100% | 300 |
What's included
- 300 practice questions for your grade, weighted to match the real exam's topic mix.
- A full 100-question timed exam simulator, built in the same proportions as the real test.
- Maths drills with fully worked solutions — every calculation shown step by step, using the same formulas and constants as the formula sheet you're given in the real exam.
- Practice by topic when you want to drill a weak area, with an explanation after every answer.
- A score report after every session showing where you're dropping marks, topic by topic.
- Works on your phone, tablet or computer — nothing to install.
- 12 months of access from the day you buy.
One price. One grade. Twelve months.
$99
$99 — one payment, for one grade (D1 or D2), with 12 months of access from purchase. That covers all 300 practice questions, the 100-question exam simulator, the maths drills with worked solutions, and every update we make to that grade's bank while your access lasts. No subscription and nothing else to pay. For scale: the state's own exam fee is $62 for Grade 1 and $81 for Grade 2, and a failed sitting means paying again — plus the wait.
Secure checkout by Stripe. Your access details are emailed to you straight after payment.