CDPH Lead Inspector/Assessor California State Practice Exam

How long must water remain in the pipe before collecting a first draw water sample?

1. 3 hours

2. 6 hours

3. 12 hours

4. 24 hours

The correct answer is: 6 hours

The requirement for water to remain in the pipe before collecting a first draw water sample is a critical protocol in lead testing to ensure that the sample reflects the potential lead levels attributed to plumbing fixtures and pipes. Water must remain stagnant in the plumbing system for a period of at least 6 hours to allow any lead that may have leached into the water from the pipes or fixtures to accumulate. By allowing this stagnation period, the sample taken is more representative of the water that would typically be consumed after the system has been undisturbed for a significant time. This helps in determining the potential risk of lead exposure from drinking water. Samples taken after a shorter period may not accurately reflect the lead concentration, as the lead may not have had sufficient time to leach into the water, thus leading to potentially misleading results. Therefore, the correct answer of 6 hours is based on established guidelines for accurately detecting lead contamination in drinking water systems.