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California D1 water distribution exam math
In short
- Exam size: the State Water Board's D1 exam has 100 questions across all subjects. Math questions are mixed in; the Board doesn't publish how many.
- Math topics: 5 areas: unit conversions and pressure; area and volume; flow, velocity and detention; chlorination and CT; and wells, pumps and power.
- Formulas: everything is solved with the Exam Conversion Sheet (revised 4/30/2026). D1 problems use 11 of its formulas, most often “Cylinder Volume (Gal) = .785 x D2 x Height or Length (Ft) x 7.48”, “Gas (lbs) = MG x mg/L x 8.34”, “Specific Capacity (GPM/Ft) = Well Yield (GPM) / Drawdown (Ft)”.
- How to study: find each topic's formulas on the sheet, work the examples on the topic pages, practice one topic at a time until most answers come out right, then mix topics in timed sets.
Math topics on the D1 exam
- Unit conversions and pressureFlow, volume, pressure/head and concentration conversions; meters; SCADA signals.250 problems in the bank
- Area and volumePipe, tank, basin, trench and wall areas and volumes; force on a valve.124 problems in the bank
- Flow, velocity and detentionQ = A x V, fill rates, detention time, surface loading.50 problems in the bank
- Chlorination and CTChlorine feed, demand and residual, hypochlorite, well and main disinfection, CT, chloramines.225 problems in the bank
- Wells, pumps and powerDrawdown, specific capacity, horsepower, efficiency, pumping cost.75 problems in the bank
What the State Water Board lists for D1 math
- D1 - D5 Ability to convert water units
- D1 - D5 Ability to convert units of volume, area, pressure, and time
- D1 - D5 Ability to convert pressure to feet of head
- D1 - D5 Ability to calculate the area of a pipe cross-section
- D1 - D5 Ability to calculate the volume of a well, storage reservoir, pipe, trench
- D1 - D5 Ability to calculate the volume of a cylinder, rectangle, and square
- D1 - D5 Ability to calculate flow rates
- D1 - D5 Ability to calculate a disinfectant dosage
- D1 - D5 Ability to calculate the well draw down
Quoted from the SWRCB Expected Range of Knowledge, Drinking Water Distribution Exam (Rev. 4/2020). These are the objectives our D1 problems practice; the document lists every objective for the grade.
Conversion sheet formulas for D1
Most used first. Each links to a worked example on the conversion sheet page.
- Cylinder Volume (Gal) = .785 x D2 x Height or Length (Ft) x 7.48100 problems
- Gas (lbs) = MG x mg/L x 8.3475 problems
- Specific Capacity (GPM/Ft) = Well Yield (GPM) / Drawdown (Ft)75 problems
- HTH Solid (lbs) = MG x mg/L x 8.34 / (Strength (%)/100)50 problems
- Liquid (Gal) = MG x mg/L x 8.34 / (Strength (%)/100 x Chemical Weight (lbs/gal))50 problems
- Dosage (mg/L) = Demand (mg/L) + Residual (mg/L)50 problems
- mg/L = lbs / (MG x 8.34)50 problems
- Area of Circle = .785 X D249 problems
- Rectangular Basin (Gal) = Length (Ft) x Width (Ft) x Height (Ft) x 7.4825 problems
- (Q) Flow (Ft3/Sec) = (A) Area (Ft2) x (V) Velocity (Ft/Sec)25 problems
- GPM = Volume (Gal) / Time (Min)25 problems
Free printable D1 worksheet
10 problems across the D1 topics, with room to work and an answer key on the last page. No sign-up; print it or save it as a PDF.
Open the D1 worksheetD1 exam math questions
How many questions are on the California D1 exam?
100, across all of the exam's subjects, according to the State Water Board's Expected Range of Knowledge for the distribution exam. Math questions are mixed in with the rest, and the Board does not publish how many there are. Check the State Water Board's operator certification page for current exam rules.
What math is on the D1 exam?
5 areas: unit conversions and pressure; area and volume; flow, velocity and detention; chlorination and CT; and wells, pumps and power. The Expected Range of Knowledge lists objectives such as the “ability to convert water units” and the “ability to calculate the well draw down”.
Which formulas do I need for the D1 exam?
The ones on the State Water Board's Exam Conversion Sheet (revised 4/30/2026). The D1 problems here use 11 of its formulas; the most common are “Cylinder Volume (Gal) = .785 x D2 x Height or Length (Ft) x 7.48”, “Gas (lbs) = MG x mg/L x 8.34”, “Specific Capacity (GPM/Ft) = Well Yield (GPM) / Drawdown (Ft)”. The conversion sheet page shows each formula with a worked example.
Is there a free D1 practice test?
Yes. The worked examples on each topic page and the printable 10-problem worksheet with answer key are free without an account. A free account adds practice from all 724 D1 problems with worked solutions, and timed sets. It covers the math only, not the whole exam.
Formulas and constants: CA Exam Conversion Sheet (revised 4/30/2026). Exam rules and the full range of knowledge: State Water Board operator certification.
WaterExamMath is independent practice software. It is not affiliated with, endorsed by or connected to the California State Water Resources Control Board. It covers the math portion of the drinking water operator exams only, not the whole exam, and passing is not guaranteed. Practice problems by WaterExamMath.