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Wells, pumps and power: California D3 water distribution operator math

Drawdown, specific capacity, horsepower, efficiency, pumping cost.

Below are 3 worked examples. Each answer is computed with the formulas and constants on the CA Exam Conversion Sheet (revised 4/30/2026), and the solution names the line it uses.

Formulas from the sheet for this topic

Example 1. A well yields 1,510 GPM. The static water level is 24 ft below ground and the pumping water level is 65 ft below ground. What is the specific capacity?

  1. A) 23.2 GPM/ft
  2. B) 0.0272 GPM/ft
  3. C) 36.8 GPM/ft
  4. D) 17.0 GPM/ft
Show the answer and worked solution

Answer: C) 36.8 GPM/ft

1. Drawdown = 65 − 24 = 41 ft. 2. Specific Capacity = Well Yield ÷ Drawdown [Sheet p.1, Pumping: "Specific Capacity (GPM/Ft) = Well Yield (GPM) / Drawdown (Ft)"] = 1,510 ÷ 41 = 36.83 GPM/ft. 3. Answer: 36.8 GPM/ft (rounded to 3 significant figures).

Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Pumping: "Specific Capacity (GPM/Ft) = Well Yield (GPM) / Drawdown (Ft)"

Example 2. A pump is 84% efficient and its motor is 86% efficient. What is the wire-to-water efficiency, in percent?

  1. A) 36.1%
  2. B) 54.2%
  3. C) 27.8%
  4. D) 72.2%
Show the answer and worked solution

Answer: D) 72.2%

1. WWE = (Pump Eff/100) × (Motor Eff/100) [Sheet p.1, Pumping: "WWE (%) = (Pump % Eff/100) x (Motor % Eff/100)"] = 0.84 × 0.86 = 0.7224. 2. The sheet labels WWE "(%)", which means you multiply the decimal by 100 to get a percent: 0.7224 × 100 = 72.24%. 3. Answer: 72.2% (rounded to 3 significant figures).

Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Pumping: "WWE (%) = (Pump % Eff/100) x (Motor % Eff/100)"

Example 3. Before pumping, the water level in a well is 177 ft below ground. After pumping for several hours it stabilizes at 241 ft below ground. What is the drawdown?

  1. A) 209 ft
  2. B) 64.0 ft
  3. C) 32.0 ft
  4. D) 418 ft
Show the answer and worked solution

Answer: B) 64.0 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. = 241 − 177 = 64 ft. 3. Answer: 64.0 ft.

Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Pumping: "Specific Capacity (GPM/Ft) = Well Yield (GPM) / Drawdown (Ft)"

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