CWS Residential Water Quality Testing 3 — Questions and Answers
Question 1: A homeowner reports blue-green staining in sinks and tubs. Which water quality parameter should be tested FIRST?
- Manganese
- Copper (Correct answer)
- Iron
- Chloride
Correct answer: Copper
Blue-green staining is a classic sign of elevated copper in water, often caused by corrosion of copper pipes.
Question 2: Which water quality test is recommended for homes built before 1986 due to older plumbing materials?
- Radon
- Lead (Correct answer)
- Arsenic
- Fluoride
Correct answer: Lead
Homes built before 1986 may have lead solder or lead pipes, making lead testing critical per EPA guidance.
Question 3: When testing for lead at the tap using the EPA's 'first-draw' protocol, how long must the water sit stagnant before sampling?
- At least 2 hours
- At least 6 hours (Correct answer)
- At least 12 hours
- At least 24 hours
Correct answer: At least 6 hours
The first-draw protocol requires at least 6 hours of stagnation to allow water contact with lead-containing plumbing before sampling.
Question 4: Radon in residential drinking water is MOST concerning when the water source is:
- A surface reservoir
- A private well in a granite or uranium-rich bedrock area (Correct answer)
- A municipal lake intake
- A rainwater collection cistern
Correct answer: A private well in a granite or uranium-rich bedrock area
Groundwater from wells in granite or uranium-rich geology can carry dissolved radon, which volatilizes during household use and becomes an inhalation hazard.
Question 5: A customer's water test shows iron at 0.5 mg/L and manganese at 0.1 mg/L. Which aesthetic issue is MOST likely reported?
- Salty or brackish taste
- Black or dark brown staining on laundry and fixtures (Correct answer)
- Rotten egg odor
- Cloudy or milky appearance
Correct answer: Black or dark brown staining on laundry and fixtures
Manganese at or above 0.05 mg/L commonly causes black or dark brown staining on fixtures, laundry, and dishwashers.
Question 6: The Langelier Saturation Index (LSI) is used to predict water's tendency to:
- Support bacterial growth
- Form or dissolve calcium carbonate scale (Correct answer)
- Remove chlorine residual
- Increase turbidity
Correct answer: Form or dissolve calcium carbonate scale
The LSI quantifies whether water is scale-forming (positive LSI) or corrosive/scale-dissolving (negative LSI) based on calcium carbonate equilibrium.
Question 7: Which of the following volatile organic compounds (VOCs) is most commonly found in residential well water near gas stations or underground storage tanks?
- Trichloroethylene (TCE)
- Benzene (Correct answer)
- Chloroform
- Atrazine
Correct answer: Benzene
Benzene is a key gasoline component and the most commonly detected VOC in groundwater near leaking underground storage tanks.
CWS Residential Water Quality Testing 3
A homeowner reports blue-green staining in sinks and tubs.
Which water quality parameter should be tested FIRST?