Texas Class D water exam practice, in English or Spanish

For new operators. The math, step by step.

Try one question · Math

About how many gallons of water fit in one cubic foot?

Tap a choice to check it.

The right choice: 7.48 gallons

One cubic foot holds about 7.48 gallons, the factor you multiply by to turn a tank's cubic feet into gallons. The tempting 8.34 is a weight, the pounds in one gallon of water, not a volume. TCEQ's conversion table lists both.

Source: TCEQ Water Supply Division, RG-379 Total Organic Carbon (TOC) Guide (revised January 2022), Appendix 4, Table A5.2 Conversions: cubic feet x 7.48 = gallons; gal x 8.34 = pounds

This is independent practice.
You book the exam at a TCEQ-approved center.

Try 7 days free

Free for 7 days. Then $29 when the 7 days end and every month until you cancel. Cancel online in your account. By starting, you accept the Terms.

You can take the Class D exam in Spanish

TCEQ offers the Class D water exam in Spanish[1]. On screen, each question has a button to read it in Spanish, and you mark the answer on the English version[2]. That is why OperadorListo shows every question in both languages, one tap apart.

Why practice the math before the exam

In 2024, 38% of Class D water exam sittings passed[3]. The exam is closed book and you can’t bring a formula sheet[1]. On OperadorListo you practice without the formula in view. TCEQ’s numbers, exam by exam.

Who makes OperadorListo

The makers of JourneyListo (journeylisto.com), practice software for the Texas electrician exams.

Free, with no account

Calculators that show every step of the math: chlorine pounds per day, round tank gallons and gpm and MGD. An extra, from the Class C exam: detention time.
The Class D exam’s formulas on one page, in Spanish with their English names.

Rather see where you stand first? Take the free check.

Frequently asked questions

Where can I practice for the Texas Class D water operator exam in Spanish?

On OperadorListo, independent practice software for the TCEQ Class D water exam: the 8 subjects TCEQ publishes[4], in Spanish and English, with every math problem worked step by step.

Do I need a card for the free week?

Yes. You enter a card at the start and nothing is charged during the 7 days. Cancel before and you pay nothing. If you stay, you pay $29 a month.

Is OperadorListo the course TCEQ requires before the exam?

No. TCEQ requires two approved courses before the exam: Basic Water Operations and Resiliency Overview[5]. OperadorListo is practice for the exam and does not replace those courses.

Will these questions be on the exam?

No. They are original practice questions, written from public sources: Texas rules, TCEQ’s pages and other government publications. The exam’s contents are confidential[6].

Sources

TCEQ, Computer-Based Testing for Occupational Licenses, Spanish exams now available by computer-based test (CBT); Authorized Aids During Licensing Exams (read November 13, 2026)
TCEQ, Spanish Instructions for Taking a CBT Exam (PDF, created Oct 2021), Instrucciones para ver la versión de las preguntas y respuestas en español (read November 13, 2026)
TCEQ Training Provider Updates 2025 (slides), Exam Analysis, slide 12, Water Occupational Licenses, Date Range 1/1/2024 - 1/1/2025 (read November 13, 2026)
TCEQ, Public Water System Operators: What Applicants for Licensing Need to Know, Need-to-Know Criteria for Class D Water Operators (read November 13, 2026)
TCEQ, Occupational Licenses: Water System Operators, Class D Licensing Requirements (read November 13, 2026)
30 TAC §30.20(a) and (h)(3); TCEQ CBT page, (a), (h)(3) (read November 13, 2026)

Reviewed November 13, 2026. Published by OperadorListo. The sources above are the authority. This is a summary in our own words: check the source before you act on it.