Complex sentence: Lead pipes can leach lead into the water, especially if certain contaminants are present; the water from Detroit Water and Sewerage had been treated well enough that the leaching from the lead pipes was at levels considered acceptable by state and federal environmental protection agencies.
Split into simpler sentences: Lead pipes can leach lead into the water, especially if certain contaminants are present. However the water from Detroit Water and Sewerage had been treated well enough that the leaching from the lead pipes was at levels considered acceptable by state and federal environmental protection agencies.