Texas, TCEQ, Water System Operator, Class D
Free Tank Volumes Practice: Texas Class D Water
Last reviewed 2026-08-01. Facts link to their official source.
Free tank volumes practice problems for the Texas Class D water operator exam. You practice rectangle and round tank volumes ending in gallons, plus the circle areas loading questions need. Every problem uses fresh numbers, checks your answer, and shows all ten worked steps with nothing skipped. Progress saves on your device.
Loading practice
One full worked example, every step shown
You practice rectangle and round tank volumes ending in gallons, plus the circle areas loading questions need. This example works rectangular basin volume in gallons from start to finish. Every number traces to the question, a named conversion, or the line before it.
1. What you know
Length: 20 ft. Width: 10 ft. Water depth: 8 ft.
2. What you need
The water the basin holds, in gallons.
3. Match the units
The dimensions are in feet, so their product is cubic feet. Each cubic foot holds 7.48 gallons, which moves the answer into gallons.
4. Choose the formula
Length times width times depth counts the cubic feet of water, and each cubic foot holds 7.48 gallons.
gallons = length x width x depth x 7.48
5. Put in the values
Put each labeled value into the formula before doing any arithmetic.
gal = 20 x 10 x 8 x 7.48
6. Track the units
The three feet multiply into cubic feet. Cubic feet then divide out through the 7.48 link, leaving gallons.
ft x ft x ft -> ft3, ft3 x gal/ft3 -> gal
7. Work it
One operation, one line.
20 x 10 = 200
200 x 8 = 1600
1600 x 7.48 = 11968
8. Round at the end
The rule here: round to the nearest whole gallon at the end. 11968 becomes 11968 gal.
9. Check the answer
11968 gallons should be well above the cubic-feet count, since each cubic foot spreads into several gallons. The unit left is gallons, which is what the question asked for.
10. What it means
This is how a drawing becomes an operating number: the basin's dimensions turn into the gallons you can dose, drain, or report.
The formulas in this module
Rectangular basin volume in gallons
gallons = length x width x depth x 7.48
Length times width times depth counts the cubic feet of water, and each cubic foot holds 7.48 gallons.
Area of a circular tank or clarifier
area = 0.785 x diameter x diameter
A circle fills 0.785 of the square drawn around it, and diameter times diameter is that square's area.
Round tank volume in gallons
gallons = 0.785 x diameter x diameter x depth x 7.48
The circle area times the depth counts the cubic feet inside the round tank, and each cubic foot holds 7.48 gallons.
Where each number comes from
- One cubic foot holds 7.48 gallons. 1 gallon is defined as 231 cubic inches. 1 cubic foot is 12 x 12 x 12 = 1728 cubic inches. 1728 divided by 231 = 7.4805, used as 7.48.
- A circle fills 0.785 of the square drawn around it. The circle area formula pi x radius squared, rewritten for diameter, becomes (pi / 4) x diameter squared. Pi divided by 4 is 0.7854, used as 0.785.
Where this fits in the official exam
- The official subject list this module serves
- Eight official Need-to-Know subjects: Rules/Regulations; Safety; General; Groundwater; Surface Water; Storage/Distribution; Disinfection; Math.
- Source: TCEQ Water Operator Exam Knowledge ('Need-to-Know Criteria for Class D Water Operators' table.)