 samples from drinking water fountains in 50 schools in new jersey were collected at specific times during a typical school day and analyzed for lead , copper , ph , alkalinity , and hardness . 
 first - draw lead and copper levels ( medians 0.010 mg / l and 0.26 mg / l , respectively ) decreased significantly after 10 min of flushing in the morning ( medians 0.005 mg / l lead and 0.068 mg / l copper ) , but levels increased significantly by lunchtime ( medians 0.007 mg / l lead and 0.12 mg / l copper ) after normal use of fountains in the morning by students . 
 corrosive water , as defined by the aggressive index , contained significantly higher levels of lead and copper ( medians 0.012 mg / l and 0.605 mg / l , respectively ) than noncorrosive water ( medians 0.005 mg / l and 0.03 mg / l , respectively).imagesp240-a 
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