T4 Water Treatment Practice Test (California)

Administered by State Water Resources Control Board (SWRCB) — Division of Drinking Water

No new objectives beyond T3; the shift is in weighting. Regulations and administrative duties rise to 35 of 100 questions.

California's certificate for running a drinking water treatment plant.

Start studying T4

Official formula sheet

T4 eligibility

To sit the T4 exam

To be certified at T4

How the T4 exam is weighted

Content areaquestions of 100
Source Water15
Water Treatment Processes20
Operation / Maintenance15
Laboratory Procedures15
Regulations / Administrative Duties35

T4 exam format

T4 pass rate

54% of examinees passed (99 of 184) from July 1, 2025 to June 30, 2026. Source: SWRCB Drinking Water Operator Certification Program, Water Treatment Exam Results (through 6/30/2026). The agency updates these tables every six months.

T4 sample question

Administrative duties: energy budget · an original practice item written only from publicly available sources, not a real exam question

A high-service pump draws 50 kW and runs 16 hours a day, every day of the year. At $0.18 per kWh, what should the annual energy budget line for this pump be?

  1. $144
  2. $4,320
  3. $37,440
  4. $52,560
Answer and working

D. $52,560

Daily energy = 50 kW × 16 h = 800 kWh, costing 800 × $0.18 = $144 a day. Over 365 days that is $52,560. $144 is one day, $4,320 is one 30-day month, and $37,440 budgets only 260 weekdays although the pump runs every day.

T4 questions answered

What do I need to sit the T4 treatment exam?
A valid T3 certificate. Three specialized courses, at least two in drinking water treatment.
How is the T4 exam weighted?
Source Water: 15; Water Treatment Processes: 20; Operation / Maintenance: 15; Laboratory Procedures: 15; Regulations / Administrative Duties: 35 (of 100 questions).
What is the recent T4 pass rate?
54%: 99 of 184 examinees passed from July 1, 2025 to June 30, 2026, summed from the agency's two half-year results tables.

What this exam covers

How to study for it here

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Other grades in this track

Grade T1 — Entry level · Grade T2 · Grade T3 · Grade T5 — Chief operator · All Water Treatment grades

Related exams

Water Distribution · Advanced Water Treatment: AWT Grade 3

Sources

Topic coverage follows Expected Range of Knowledge for Drinking Water Treatment 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.