Secondary Constituents
Secondary constituents are regulated in public drinking water. They are called "secondary," instead of primary, because they have no adverse health effects.
| Constituent | Secondary Maximum Contaminant Level (mg/L except where stated otherwise) | Effects |
| Chloride | 300 | salty taste |
| Color | 15 color units | tinted water |
| Copper | 1.0 | metallic taste; blue-green staining |
| Corrosivity | Non-corrosive | metallic taste; staining |
| Fluoride | 2.0 | tooth discoloration |
| Foaming Agents | 0.2 | frothy or cloudy water; bitter taste |
| Hydrogen Sulfide | 0.05 | rotten-egg odor or taste |
| Iron | 0.2 | rusty color; sediment; metallic taste; staining |
| Manganese | 0.05 | dark color; staining; bitter metallic taste |
| Odor | 3 Threshold Odor Number | rotten-egg odor |
| pH | >7.0 | bitter taste; deposits; slippery or soapy feel |
| Silver | 0.1 | skin discoloration; greying of the white portion of the eye |
| Sulfate | 300 | salty taste |
| Total Dissolved Solids (TDS) | 1,000 | hardness; deposits; colored water; staining salty taste |
| Zinc | 5.0 | metallic taste |