The secondary maximum contaminant levels for public water systems are as follows:
| Contaminant | Level |
|---|---|
| Aluminum | 0.05 to 0.2 mg/l. |
| Chloride | 250 mg/l. |
| Color | 15 color units. |
| Copper | 1.0 mg/l. |
| Corrosivity | Non-corrosive. |
| Fluoride | 2.0 mg/l. |
| Foaming agents | 0.5 mg/l. |
| Iron | 0.3 mg/l. |
| Manganese | 0.05 mg/l. |
| Odor | 3 threshold odor number. |
| pH | 6.5-8.5. |
| Silver | 0.1 mg/l. |
| Sulfate | 250 mg/l. |
| Total dissolved solids (TDS) | 500 mg/l. |
| Zinc | 5 mg/l. |
These levels represent reasonable goals for drinking water quality. The States may establish higher or lower levels which may be appropriate dependent upon local conditions such as unavailability of alternate source waters or other compelling factors, provided that public health and welfare are not adversely affected.
[44 FR 42198, July 19, 1979, as amended at 51 FR 11412, Apr. 2, 1986; 56 FR 3597, Jan. 30, 1991]