D1 water distribution math worksheet
California D1 water distribution operator exam · 10 problems
Name: ______________________________ Date: ______________
Use the CA Exam Conversion Sheet (revised 4/30/2026) and a calculator.
1. A flow meter reads 6.6 cubic feet per second (CFS). What is the flow in GPM?
Unit conversions and pressure
- A) 396 GPM
- B) 49.4 GPM
- C) 1,480 GPM
- D) 2,960 GPM
2. A chlorinator feeds 638 lbs/day into 15 MGD. The residual measured after the contact time is 0.9 mg/L. What is the chlorine demand?
Chlorination and CT
- A) 2.10 mg/L
- B) 5.10 mg/L
- C) 4.20 mg/L
- D) 6.00 mg/L
3. A storage tank gains 720,000 gallons in 12.5 hours while nothing is drawn from it. What is the average inflow in GPM?
Flow, velocity and detention
- A) 16.0 GPM
- B) 960 GPM
- C) 40.0 GPM
- D) 57,600 GPM
4. A rectangular basin is 90 ft long and 50 ft wide, with water 14.5 ft deep. How many gallons does it hold?
Area and volume
- A) 33,700 gal
- B) 65,300 gal
- C) 488,000 gal
- D) 244,000 gal
5. The static water level in a well is 67 ft below ground. While the pump runs, the drawdown is 77 ft. How far below ground is the pumping water level?
Wells, pumps and power
- A) 77.0 ft
- B) 144 ft
- C) 10.0 ft
- D) 221 ft
6. An industrial customer's meter, which registers in CCF, read 41922 and, 35 days later, 44125. What was the average use in gallons per day?
Unit conversions and pressure
- A) 47,100 GPD
- B) 1,960 GPD
- C) 23,600 GPD
- D) 6,290 GPD
7. A well pumps 1,225 GPM around the clock. How many lbs/day of chlorine are needed for a dose of 3.5 mg/L?
Chlorination and CT
- A) 6.17 lbs/day
- B) 2.15 lbs/day
- C) 51.5 lbs/day
- D) 79.7 lbs/day
8. Water flows through a 24-inch main at 5 ft/sec. What is the flow in GPM?
Flow, velocity and detention
- A) 3,520 GPM
- B) 7,050 GPM
- C) 5,290 GPM
- D) 117 GPM
9. A cylindrical storage tank is 70 ft in diameter with water 40 ft deep. How many gallons does it hold?
Area and volume
- A) 1,150,000 gal
- B) 4,600,000 gal
- C) 154,000 gal
- D) 16,400 gal
10. Before pumping, the water level in a well is 254 ft below ground. After pumping for several hours it stabilizes at 321 ft below ground. What is the drawdown?
Wells, pumps and power
- A) 67.0 ft
- B) 575 ft
- C) 33.5 ft
- D) 288 ft
Answer key: D1 water distribution math worksheet
1. D) 2,960 GPM
1. 1 CFS = 448.8 GPM [Sheet p.1, Units and Conversion Factors, row 7: "1 CFS = 448.8 GPM"]. 2. GPM = 6.6 CFS × 448.8 = 2,962.08 GPM. 3. Answer: 2,960 GPM (rounded to 3 significant figures).
Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Units and Conversion Factors, row 7: "1 CFS = 448.8 GPM"
2. C) 4.20 mg/L
1. Dose (mg/L) = lbs ÷ (MG × 8.34) [Sheet p.1, Solutions: "mg/L = lbs / (MG x 8.34)"] = 638 ÷ (15 × 8.34) = 5.1 mg/L. 2. Dosage = Demand + Residual [Sheet p.1, Chlorination: "Dosage (mg/L) = Demand (mg/L) + Residual (mg/L)"], so Demand = 5.1 − 0.9 = 4.2 mg/L. 3. Answer: 4.20 mg/L (rounded to 3 significant figures).
Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Solutions: "mg/L = lbs / (MG x 8.34)"; p.1, Chlorination: "Dosage (mg/L) = Demand (mg/L) + Residual (mg/L)"
3. B) 960 GPM
1. Time in minutes = 12.5 hrs × 60 min/hr = 750 min [Sheet p.1, Units and Conversion Factors, rows 8-9: 1 day = 24 hrs = 1440 min, so 1440 / 24 = 60 min/hr]. 2. GPM = Volume ÷ Time [Sheet p.1, Flow & Velocity: "GPM = Volume (Gal) / Time (Min)"] = 720,000 ÷ 750 = 960 GPM. 3. Answer: 960 GPM.
Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Units and Conversion Factors, rows 8-9: 1 day = 24 hrs = 1440 min, so 1440 / 24 = 60 min/hr; p.1, Flow & Velocity: "GPM = Volume (Gal) / Time (Min)"
4. C) 488,000 gal
1. Rectangular Basin (Gal) = L × W × H × 7.48 [Sheet p.1, Area and Volume: "Rectangular Basin (Gal) = Length (Ft) x Width (Ft) x Height (Ft) x 7.48"]. 2. = 90 × 50 × 14.5 × 7.48 = 488,070 gal. 3. Answer: 488,000 gal (rounded to 3 significant figures).
Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Area and Volume: "Rectangular Basin (Gal) = Length (Ft) x Width (Ft) x Height (Ft) x 7.48"
5. B) 144 ft
1. Drawdown = pumping water level − static water level (the denominator of [Sheet p.1, Pumping: "Specific Capacity (GPM/Ft) = Well Yield (GPM) / Drawdown (Ft)"]), so pumping water level = static water level + drawdown. 2. = 67 + 77 = 144 ft below ground. 3. Answer: 144 ft.
Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Pumping: "Specific Capacity (GPM/Ft) = Well Yield (GPM) / Drawdown (Ft)"
6. A) 47,100 GPD
1. Use = 44125 − 41922 = 2203 CCF. 2. 1 CCF = 748 Gal [Sheet p.1, Units and Conversion Factors, row 6: "1 CCF = 748 Gal"]: 2203 × 748 = 1,647,844 gal. 3. GPD = 1,647,844 gal ÷ 35 days = 47,081 GPD. 4. Answer: 47,100 GPD (rounded to 3 significant figures).
Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Units and Conversion Factors, row 6: "1 CCF = 748 Gal"
7. C) 51.5 lbs/day
1. Flow = 1,225 ÷ 694.4 = 1.764 MGD [Sheet p.1, Units and Conversion Factors, row 29: "1 MGD = 694.4 GPM"]. 2. Gas (lbs) = MG × mg/L × 8.34 [Sheet p.1, Chlorination: "Gas (lbs) = MG x mg/L x 8.34"] = 1.764 × 3.5 × 8.34 = 51.49 lbs/day. 3. Answer: 51.5 lbs/day (rounded to 3 significant figures).
Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Units and Conversion Factors, row 29: "1 MGD = 694.4 GPM"; p.1, Chlorination: "Gas (lbs) = MG x mg/L x 8.34"
8. B) 7,050 GPM
1. A = .785 × D² [Sheet p.1, Area and Volume: "Area of Circle = .785 X D2"] = .785 × (24 ÷ 12)² = 3.14 ft² [12 in = 1 ft]. 2. Q = A × V [Sheet p.1, Flow & Velocity: "(Q) Flow (Ft3/Sec) = (A) Area (Ft2) x (V) Velocity (Ft/Sec)"] = 3.14 × 5 = 15.7 ft³/sec. 3. 1 CFS = 448.8 GPM [Sheet p.1, Units and Conversion Factors, row 7: "1 CFS = 448.8 GPM"]: 15.7 × 448.8 = 7,046.16 GPM. 4. Answer: 7,050 GPM (rounded to 3 significant figures). 5. If you used 1.55 CFS per MGD (Units row 28) and 694.4 GPM per MGD (row 29) instead of 448.8 GPM per CFS (row 7), you get 7,030 GPM. The sheet prints both factors, so either answer is right; pick the option closest to yours.
Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Area and Volume: "Area of Circle = .785 X D2"; p.1, Flow & Velocity: "(Q) Flow (Ft3/Sec) = (A) Area (Ft2) x (V) Velocity (Ft/Sec)"; p.1, Units and Conversion Factors, row 7: "1 CFS = 448.8 GPM"
9. A) 1,150,000 gal
1. Cylinder Volume (Gal) = .785 × D² × Height × 7.48 [Sheet p.1, Area and Volume: "Cylinder Volume (Gal) = .785 x D2 x Height or Length (Ft) x 7.48"]. 2. = .785 × 70 × 70 × 40 × 7.48 = 1,150,873 gal. 3. Answer: 1,150,000 gal (rounded to 3 significant figures).
Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Area and Volume: "Cylinder Volume (Gal) = .785 x D2 x Height or Length (Ft) x 7.48"
10. A) 67.0 ft
1. Drawdown = pumping water level − static water level (the denominator of [Sheet p.1, Pumping: "Specific Capacity (GPM/Ft) = Well Yield (GPM) / Drawdown (Ft)"]). 2. = 321 − 254 = 67 ft. 3. Answer: 67.0 ft.
Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Pumping: "Specific Capacity (GPM/Ft) = Well Yield (GPM) / Drawdown (Ft)"