CPO Pool Calculations and Formulas 3

Question 1

The standard weight of water used in pool chemical dosage calculations is:

Accepted Answer

8.34 lbs per gallon

Answer

Water weighs 8.34 lbs per gallon, which is the standard value used when calculating parts per million in pool water.

Question 2

Using the formula: lbs = (ppm × gallons × 8.34) / (% × 10,000), how many pounds of calcium hypochlorite (65% available chlorine) are needed to raise a 10,000-gallon pool by 2 ppm?

Accepted Answer

0.26 lbs

Answer

lbs = (2 × 10,000 × 8.34) / (65 × 10,000) = 166,800 / 650,000 ≈ 0.26 lbs of cal hypo.

Question 3

A pool has combined chlorine (chloramines) measuring 0.5 ppm. To achieve breakpoint chlorination, the free chlorine level must reach at least:

Accepted Answer

5.0 ppm

Answer

Breakpoint chlorination requires free chlorine to reach 10 times the combined chlorine level: 10 × 0.5 = 5.0 ppm.

Question 4

Which chemical is typically used to LOWER pH in a swimming pool?

Accepted Answer

Muriatic acid (hydrochloric acid)

Answer

Muriatic acid (HCl) or dry acid (sodium bisulfate) is used to lower pH because both are acidic compounds.

Question 5

Sodium hypochlorite solution at 12.5% strength weighs 10.0 lbs per gallon. How many ounces of actual (available) chlorine are in 1 gallon?

Accepted Answer

20 oz

Answer

12.5% of 10.0 lbs = 1.25 lbs of available chlorine × 16 oz/lb = 20 oz of available chlorine per gallon.

CPO (Certified Pool Operator Exam) Practice Test

CPO (Certified Pool Operator Exam) Practice Test

CPO Pool Calculations and Formulas 3