Environmental Protection Agency (EPA) Lead Risk Assessor Practice Exam

How long should water sit motionless before being sampled?

1. 1 hour

2. 6 hours

3. 12 hours

4. At least 6 hours, first thing in the morning

The correct answer is: At least 6 hours, first thing in the morning

Water should sit motionless for at least 6 hours before being sampled because this time frame allows for a reliable assessment of lead levels originating from plumbing materials, such as lead pipes or solder. When water remains stagnant in the pipes for this duration, it can absorb lead leached from these materials, providing a more accurate representation of potential exposure levels when the water is used for drinking or cooking. Sampling at this interval, particularly first thing in the morning, ensures that the water has had sufficient time to accumulate any contaminants that may be present in the plumbing system. This practice is crucial for assessing lead exposure risks accurately, especially in homes built before the lead pipe ban was implemented. This measure helps ensure that the sampling reflects the actual water quality that residents may consume after prolonged periods of inactivity in the plumbing.