Practice Test Geeks(CWS) Certified Water Specialist Practice Test
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Residential Water Quality Testing Flashcards

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

Read the first 7 Residential Water Quality Testing flashcards as text

  1. Which analytical method is the EPA-approved standard for measuring arsenic in drinking water at low concentrations?

    Answer: Inductively coupled plasma mass spectrometry (ICP-MS)

    ICP-MS provides the sensitivity required to detect arsenic at the 10 µg/L MCL and below, making it the preferred EPA method.

  2. A private well test report lists 'total hardness' at 350 mg/L as CaCO3. How would this water be classified?

    Answer: Very hard

    Water above 300 mg/L as CaCO3 is classified as very hard, which can cause significant scale buildup in appliances and plumbing.

  3. What is the purpose of a holding time limit on water samples sent to a laboratory?

    Answer: To ensure analyte concentrations remain representative of conditions at collection

    Holding time limits ensure that physical, chemical, or biological changes during storage do not alter the test results from what existed at collection.

  4. Hydrogen sulfide (H2S) causes a 'rotten egg' odor in water. Which field condition requires immediate on-site testing for H2S rather than lab analysis?

    Answer: H2S is highly volatile and off-gasses rapidly from the sample

    Hydrogen sulfide is a dissolved gas that rapidly volatilizes from water samples, requiring field measurement within minutes of collection.

  5. A water sample from a residential well shows a heterotrophic plate count (HPC) of 800 CFU/mL. What does this indicate?

    Answer: Elevated bacterial population suggesting possible treatment or system issue

    HPC above 500 CFU/mL suggests elevated bacterial activity that may indicate inadequate disinfection, biofilm growth, or system contamination.

  6. Which federal regulation requires community water systems to test for over 80 contaminants and notify customers of results annually?

    Answer: Safe Drinking Water Act (SDWA) Consumer Confidence Report Rule

    The Consumer Confidence Report (CCR) Rule under the SDWA requires annual water quality reports to be distributed to customers of community water systems.

  7. When should a homeowner collect a water sample for bacteriological testing after shock chlorinating a well?

    Answer: After running water until no chlorine odor is detectable

    Residual chlorine must be fully flushed from the system before sampling, or it will suppress bacteria and produce a falsely negative result.