Water Chemistry & Quality Control Flashcards

After a fecal accident in a pool, the CDC recommends raising free chlorine to what level (at pH 7.5) to inactivate non-Crypto pathogens?

Answer: 2 ppm for 30 minutes

For a formed stool fecal accident, CDC recommends raising free chlorine to 2 ppm at pH 7.5 and maintaining it for at least 25–30 minutes before reopening.

What does a high ORP (Oxidation-Reduction Potential) reading indicate about pool water?

Answer: Strong sanitizing ability of the water

A high ORP (ideally 650–750 mV) indicates that the water has a strong oxidizing capacity and is effective at killing pathogens.

Muriatic acid (hydrochloric acid) is added to pool water to accomplish which goal?

Answer: Lower pH and total alkalinity

Muriatic acid lowers both pH and total alkalinity, making it the primary chemical for reducing these levels when they are too high.

Sodium thiosulfate is used in aquatic facility management primarily to:

Answer: Neutralize excess chlorine

Sodium thiosulfate is a chlorine neutralizer used to quickly reduce dangerously high chlorine levels in pool water.

What is the MOST accurate description of 'superchlorination'?

Answer: Adding a large dose of chlorine (typically 10 ppm or more) to oxidize contaminants

Superchlorination involves adding a large dose of chlorine (10 ppm or more) to oxidize organic contaminants, chloramines, and algae.

Which test should be performed FIRST when troubleshooting cloudy pool water?

Answer: Free chlorine and pH

Free chlorine and pH are tested first because low chlorine or improper pH are the most common causes of cloudy water and affect all other chemistry.

Phosphates in pool water are a concern because they:

Answer: Serve as nutrients that promote algae growth

Phosphates act as fertilizers for algae, so elevated phosphate levels can fuel algae blooms even when chlorine is adequate.