Disinfection and Sanitizers Flashcards
7 cards from real CPO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Disinfection and Sanitizers flashcards as text
At a pool pH of 7.5, approximately what percentage of free chlorine exists as the effective hypochlorous acid (HOCl) form?
Answer: About 50%
At pH 7.5, the equilibrium between HOCl and OCl⁻ is approximately 50/50, making pH 7.5 a balance point for disinfection efficiency.
Why is cyanuric acid (CYA) added to outdoor pools?
Answer: To protect chlorine from ultraviolet (UV) sunlight degradation
CYA bonds to free chlorine, shielding it from UV radiation and extending its useful life in outdoor pools.
What is the generally accepted maximum recommended level of cyanuric acid in a swimming pool?
Answer: 100 ppm
Above 100 ppm, cyanuric acid over-stabilizes chlorine, significantly reducing its disinfection effectiveness (chlorine lock).
What is the only reliable way to reduce excessively high cyanuric acid levels in a pool?
Answer: Partially drain and refill with fresh water
CYA does not degrade or filter out; diluting the water by partial drain-and-refill is the only practical way to lower it.
When pool pH drops below 7.2, what is the primary operational concern?
Answer: Corrosion of equipment, surfaces, and swimmer discomfort
Low pH (acidic conditions) corrodes metal fittings, etches plaster, degrades gaskets, and causes eye/skin irritation.
What is the primary function of total alkalinity (TA) in pool water chemistry?
Answer: Buffer pH against rapid changes
Total alkalinity acts as a pH buffer, resisting sudden swings in pH caused by added chemicals or bather load.
At a high pH of 8.2, free chlorine's disinfecting effectiveness is reduced because:
Answer: The hypochlorite ion (OCl⁻) dominates and is far less effective than HOCl
At pH 8.2, over 90% of free chlorine shifts to the OCl⁻ ion form, which is approximately 100 times less effective at killing pathogens than HOCl.