Pool Calculations and Formulas Questions and Answers Flashcards

A pool has a total chlorine reading of 3.5 ppm and a free chlorine reading of 2.5 ppm. What is the combined chlorine level?

Answer: 1.0 ppm

Combined chlorine equals total chlorine minus free chlorine: 3.5 minus 2.5 equals 1.0 ppm, indicating elevated chloramines.

How many gallons of water are in a pool that measures 50 feet long, 25 feet wide, with a shallow end of 3 feet and a deep end of 9 feet?

Answer: 56,100 gallons

Average depth equals (3 plus 9) divided by 2 which is 6 feet. Volume equals 50 times 25 times 6 times 7.48 which equals 56,100 gallons.

What is the total dynamic head if static head is 15 feet, friction head loss is 22 feet, and velocity head is 1 foot?

Answer: 38 feet

TDH equals static head plus friction head plus velocity head: 15 plus 22 plus 1 equals 38 feet.

A 80,000-gallon pool needs superchlorination. Combined chlorine reads 0.8 ppm. Approximately how much sodium hypochlorite (12.5 percent) is needed?

Answer: 4.3 gallons

Breakpoint requires 10 times the combined chlorine level (8 ppm rise). Using standard dosing for 12.5 percent sodium hypochlorite, approximately 4.3 gallons is needed.

What is the surface area of an oval pool that measures 40 feet long and 20 feet wide?

Answer: 628 square feet

Oval surface area equals pi times half-length times half-width: 3.14 times 20 times 10 equals 628 square feet.

If a pool loses 1 inch of water per day to evaporation, how many gallons per day is that for a 2,000 square foot pool?

Answer: 1,247 gallons

One inch equals 1/12 foot. Volume equals 2,000 square feet times 1/12 foot times 7.48 gallons per cubic foot, which equals approximately 1,247 gallons per day.