Practice Test Geeks(CPI) Certified Pool & Spa Inspector Practice Test
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Water Balance & Chemical Testing Flashcards

7 cards from real CPI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Water Balance & Chemical Testing flashcards as text

  1. A pool water sample turns yellow when orthotolidine (OTO) reagent is added. This color change indicates the presence of:

    Answer: Total chlorine

    OTO reagent reacts with total chlorine (both free and combined) to produce a yellow color, but does not distinguish between the two forms.

  2. When testing calcium hardness using a titration test kit, the endpoint is typically indicated by a color change from:

    Answer: Red to blue

    In the EDTA titration method for calcium hardness, the indicator dye changes from red/wine to blue at the titration endpoint.

  3. A pool inspector finds a residential pool with a pH of 8.4 and free chlorine of 3.0 ppm. The effective hypochlorous acid (HOCl) percentage at this pH is approximately:

    Answer: 10%

    At pH 8.4, only about 10% of free chlorine exists as the active HOCl form; the rest is the less effective hypochlorite ion (OCl⁻).

  4. Which of the following factors is NOT directly used to calculate the Langelier Saturation Index?

    Answer: Cyanuric acid concentration

    The LSI uses pH, temperature, calcium hardness, total alkalinity, and TDS — cyanuric acid is not a direct component of the LSI formula.

  5. An inspector notes that a pool with a salt chlorine generator shows a 'low salt' warning despite the operator recently adding salt. The FIRST thing to check is:

    Answer: The pump flow rate and cell cleanliness

    Salt cell sensors require adequate flow and clean cell plates to accurately read salinity; a clogged cell or low flow can trigger false low-salt warnings.

  6. What is the primary purpose of testing for phosphates in pool water?

    Answer: Phosphates are a nutrient source that promotes algae growth

    Phosphates serve as a key nutrient for algae; elevated levels can fuel algae blooms even when sanitizer levels appear adequate.

  7. A pool inspector finds iron levels at 0.5 ppm in pool water. The MOST likely visual symptom this could cause is:

    Answer: Reddish-brown staining on pool surfaces

    Iron above 0.2–0.3 ppm can oxidize when chlorine is added and precipitate, causing reddish-brown staining on pool surfaces and equipment.