The maximum permissible level of a contaminant in water which is delivered to the free flowing
outlet of the ultimate user of a public water system, except in the case of turbidity where the
maximum permissible level is measured at the point of entry to the distribution system.
Contaminants added to the water under circumstances controlled by the user, except those
resulting from corrosion of piping and plumbing caused by water quality, are excluded from this