NASCO Water Chemistry & Quality Control 3

Question 1

Which condition is MOST likely to cause a rapid drop in pool water pH?

Accepted Answer

Heavy rain diluting pool water

Answer

Heavy rainfall, which is slightly acidic, dilutes the pool and introduces acid that lowers pH rapidly.

Question 2

Breakpoint chlorination requires adding chlorine to reach how many times the combined chlorine level?

Accepted Answer

7.6 times

Answer

Breakpoint chlorination requires adding enough chlorine so that free chlorine reaches approximately 7.6 times the combined chlorine level to destroy chloramines.

Question 3

What is the primary purpose of maintaining proper calcium hardness in pool water?

Accepted Answer

To prevent corrosion of surfaces and equipment

Answer

Proper calcium hardness (200–400 ppm) prevents corrosive water from dissolving calcium from plaster, grout, and metal fittings.

Question 4

What health hazard is most directly associated with elevated combined chlorine (chloramine) levels?

Accepted Answer

Eye and respiratory irritation

Answer

Chloramines, especially nitrogen trichloride, are responsible for the characteristic 'pool smell' and cause eye, skin, and respiratory irritation.

Question 5

Which factor does NOT directly affect the chlorine demand of a pool?

Accepted Answer

Pool depth

Answer

Pool depth does not directly affect chlorine demand; bather load, sunlight (UV), algae, and organic contaminants all consume chlorine.

(NASCO) National Aquatic Safety Company Aquatic Facility Operator Certification Practice Test

(NASCO) National Aquatic Safety Company Aquatic Facility Operator Certification Practice Test

NASCO Water Chemistry & Quality Control 3