Water Quality & Treatment Standards Flashcards

What is the recommended cyanuric acid (stabilizer) concentration range for outdoor residential pools?

Answer: 30–50 ppm

Cyanuric acid should be kept between 30–50 ppm to effectively stabilize chlorine without over-inhibiting its sanitizing ability.

A pool inspector notices the water is cloudy but the chlorine reading is within range. Which parameter should be checked next?

Answer: Filtration turnover rate and filter condition

Cloudy water with adequate chlorine typically indicates inadequate filtration, a dirty filter, or insufficient turnover rate.

Which condition describes 'combined chlorine' (chloramines) in pool water?

Answer: Chlorine bound to ammonia or nitrogen compounds

Combined chlorine forms when free chlorine reacts with ammonia or nitrogenous waste, producing chloramines that cause odor and eye irritation.

What is the minimum free chlorine level recommended by the Model Aquatic Health Code (MAHC) for a public pool?

Answer: 1.0 ppm

The MAHC recommends a minimum free chlorine level of 1.0 ppm for public pools to ensure adequate disinfection.

An inspector finds a pool's total alkalinity at 220 ppm. What is the primary concern?

Answer: pH will resist adjustment and scale formation is likely

High total alkalinity (above 180 ppm) causes pH to resist change ('pH lock') and promotes calcium carbonate scale formation.

Breakpoint chlorination requires adding chlorine to achieve what ratio relative to combined chlorine?

Answer: 7.6:1 (approximately 10 times)

Breakpoint chlorination requires adding approximately 7.6–10 times the combined chlorine level to oxidize and destroy chloramines.

Which chemical is used to LOWER pool water pH?

Answer: Muriatic acid (hydrochloric acid)

Muriatic acid (hydrochloric acid) is the most common chemical used to lower pH in pool water.