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Unit conversions and pressure: California D2 water distribution operator math

Flow, volume, pressure/head and concentration conversions; meters; SCADA signals.

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. An industrial customer's meter, which registers in CCF, read 14912 and, 28 days later, 15318. What was the average use in gallons per day?

  1. A) 1,450 GPD
  2. B) 5,400 GPD
  3. C) 10,800 GPD
  4. D) 452 GPD
Show the answer and worked solution

Answer: C) 10,800 GPD

1. Use = 15318 − 14912 = 406 CCF. 2. 1 CCF = 748 Gal [Sheet p.1, Units and Conversion Factors, row 6: "1 CCF = 748 Gal"]: 406 × 748 = 303,688 gal. 3. GPD = 303,688 gal ÷ 28 days = 10,846 GPD. 4. Answer: 10,800 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"

Example 2. A pressure gauge is mounted 7.5 ft above the floor of a storage tank and reads 8.5 psi. How deep is the water in the tank, measured from the floor?

  1. A) 54.2 ft
  2. B) 19.6 ft
  3. C) 27.1 ft
  4. D) 12.1 ft
Show the answer and worked solution

Answer: C) 27.1 ft

1. 1 PSI = 2.31 Ft [Sheet p.1, Units and Conversion Factors, row 31: "1 PSI = 2.31 Ft"]: water above the gauge = 8.5 × 2.31 = 19.635 ft. 2. Add the gauge height: 19.635 + 7.5 = 27.135 ft. 3. Answer: 27.1 ft (rounded to 3 significant figures).

Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Units and Conversion Factors, row 31: "1 PSI = 2.31 Ft"

Example 3. A flow transmitter is scaled 4 mA = 0 GPM and 20 mA = 5,800 GPM. The SCADA input reads 15.8 mA. What flow does that represent?

  1. A) 4,580 GPM
  2. B) 5,730 GPM
  3. C) 3,420 GPM
  4. D) 4,280 GPM
Show the answer and worked solution

Answer: D) 4,280 GPM

1. Process Units = (Live Signal − 4 mA) × Process Range ÷ 16 mA [Sheet p.1, Electrical/SCADA: "Process Units = (Live Signal (mA) - 4 mA) x Process Range / 16 mA"]. 2. (15.8 − 4) = 11.8 mA; 11.8 × 5,800 ÷ 16 = 4,277.5 GPM. 3. Answer: 4,280 GPM (rounded to 3 significant figures).

Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Electrical/SCADA: "Process Units = (Live Signal (mA) - 4 mA) x Process Range / 16 mA"

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