Last-hour review
California D2 last-hour refresher
Carry the units. Trace the water. California D2; ERK Rev. April 2020; conversion sheet revised April 30, 2026. Selected last-hour study reminders, not complete exam coverage.
Free edition · 2 of 8 sections
Start with something useful.
Flow, velocity, and storage
Q = A × velocity. For ft³/s, use area in ft² and velocity in ft/s. Rearrange to velocity = Q ÷ A.
Rectangular volume = length × width × depth. Cylinder volume = 0.785 × diameter² × height. With dimensions in feet, multiply ft³ by 7.48 for gallons.
Dose, demand, residual
Dose = demand + residual. Rearrange to demand = dose − residual. The amount added and the amount remaining are not the same quantity.
lb/day = MGD × mg/L × 8.34. Chemical strength corrections require the strength as a fraction, such as percentage ÷ 100.
Two free sections from edition v2026-09-05. Independent AI edition review: 2026-09-05. Review method and corrections.
Full edition · 8 sections
One last, focused look.
$2.99 USD · one-time
- Eight compact sections on important, easily confused ideas.
- One-page PDF with selectable text and clickable sources.
- Larger-text PNG for reading on your phone.
- Independent AI review—not described as human or expert review.
Included with a qualifying paid purchase for this same exam—even if your practice period has ended. Sign in with that account; we check before asking you to pay.
Free or fully discounted access does not qualify. Refunded or disputed payments lose download access. This purchase is for this edition, not a subscription or a promise of future updates.
Full refund requests within seven days. Personal study use only.
Selected reminders, not a full syllabus, official exam aid, or professional advice. Check your exam version and permitted materials. Never take this sheet into an exam unless the provider expressly permits it.