Question 1001 of 229 · California Water Distribution Operator Exam
Why is a new or repaired water main disinfected before it is placed in service?
Exactly one answer is correct.
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Correct answer to question 1001
- A: To inactivate pathogens that entered the pipe during construction or repair
Explanation
Construction exposes pipe, fittings and trench water to soil and other contamination, so the main must be disinfected before it serves customers. Flushing and pressure testing do different jobs.
More questions: Disinfection
- 1002Under the AWWA C651 continuous-feed method, what is the minimum chlorine concentration in the new main at the start of the contact period?
- 1003Under the AWWA C651 slug method, which dose and contact time apply?
- 1004After the 24-hour contact period of the continuous-feed method, what free chlorine residual must remain in the main?
- 1005Why should a new main be flushed before the disinfectant is added?
- 1006Heavily chlorinated water flushed from a main must be dechlorinated before it reaches a storm drain or creek. Which chemical is commonly used?
- 1007Approximately what percentage of available chlorine does calcium hypochlorite (HTH) contain?