CWD CWD Well Maintenance & Rehabilitation 2 — Questions and Answers
Question 1: Acid treatment of a water well is most effective for which type of fouling?
- Iron bacteria colonies
- Calcium carbonate and mineral scale deposits (Correct answer)
- Sand infiltration
- Organic matter buildup
Correct answer: Calcium carbonate and mineral scale deposits
Acid treatment (typically hydrochloric or muriatic acid) is most effective at dissolving calcium carbonate and mineral scale deposits that block well screens and the surrounding formation.
Question 2: A step-drawdown test is used primarily to:
- Determine aquifer boundaries
- Evaluate well efficiency and identify non-linear head losses (Correct answer)
- Measure aquifer storativity
- Test pump motor amperage
Correct answer: Evaluate well efficiency and identify non-linear head losses
A step-drawdown test pumps a well at sequentially increasing rates to separate aquifer losses from well losses, determining well efficiency and identifying turbulent (non-linear) head losses.
Question 3: What is the minimum waiting period after shock chlorination before a well can be returned to domestic service according to standard US practice?
- 1 hour
- 12 hours
- At least 24 hours, plus a clear bacteriological test (Correct answer)
- 72 hours regardless of test results
Correct answer: At least 24 hours, plus a clear bacteriological test
Standard practice requires waiting at least 24 hours for the chlorine to dissipate and then passing a clear bacteriological test (absent for total coliform and E. coli) before returning the well to service.
Question 4: Which indicator best signals that a submersible pump is wearing out rather than the well declining?
- Decreasing static water level
- Pump amp draw increases while yield decreases (Correct answer)
- Sand in the water
- Water pressure fluctuates with weather
Correct answer: Pump amp draw increases while yield decreases
Increasing amp draw combined with decreasing yield indicates pump impeller wear, as a worn pump draws more current to overcome internal bypass while producing less water.
Question 5: Polyphosphate sequestering agents added to well water are used to:
- Disinfect the water supply
- Prevent iron and manganese from staining fixtures (Correct answer)
- Increase well yield
- Remove nitrates
Correct answer: Prevent iron and manganese from staining fixtures
Polyphosphate sequestering agents chemically bind iron and manganese ions, keeping them in solution and preventing oxidation that causes staining on fixtures and laundry.
Question 6: When a well screen is corroded beyond rehabilitation, the recommended remedy is:
- Add chlorine annually
- Install a liner or sleeve, or construct a replacement well (Correct answer)
- Increase pump setting depth
- Install a whole-house filter only
Correct answer: Install a liner or sleeve, or construct a replacement well
A corroded well screen that cannot be rehabilitated requires either installing a well liner/sleeve to bypass the damaged section or constructing a new replacement well.
CWD CWD Well Maintenance & Rehabilitation 2
Acid treatment of a water well is most effective for which type of fouling?