Lead In Drinking Water

The water from a drinking fountain school was tested in late August and was found to contain unacceptable levels of lead. However, the water was tested again after the students return to school in September, and was tried under the maximum allowable concentration. Propose a possible explanation for this difference. Suppose that the school was used during the summer and that no pipes have been replaced.

The water dissolves the lead-containing materials very slowly, so if the water remained unused in the pipes throughout the summer, or even several days, he would have the option of dissolving lead solder (lead / tin) and brass plumbing parts (many brass alloys contain lead and a few% using machining). Once the school is occupied, the water would be used regularly, so he would not sit in the pipes very long, so there is less time to run to dissolve in water and concentration was measured lower.

Maximum allowable concentration is not good in itself. Maybe they changed the filter in the fountain? However, if the max and they changed the filter, there is a serious problem somewhere. Drinking water should not be any way that flows through lead pipes.