How can the concentration of lead in drinking water change?
The water from a school drinking fountain was tested in late August and was found to contain an unacceptable concentration of lead. However, the water was tested again, after the students returned to school in September, and was found to be under the maximum allowable concentration. Suggest a possible explanation for this difference. Assume that the school was unused over the summer and that none of the pipes were replaced.
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Filed under: Water Filters
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The water only dissolves the lead-containing materials very slowly, so if water sat idle in the pipes all summer, or even several days, it would have had a chance to dissolve lead from solder (lead/tin) and brass plumbing parts (many brass alloys contain a few % lead to aid machining). Once the school is occupied, the water would be being used regularly, so it would not sit in the pipes very long, thus there would be less time for lead to disolve into the water and the measured concentration would be lower.
Maximum allowable concentration isn’t good within itself. Maybe they changed the filter in the fountain? Still, if it’s at the max and they did change the filter, there’s a serious problem somewhere. Drinking water shouldn’t be flowing in lead pipes anyways.