Water Experiments and Demonstrations National Secondary Drinking Water Standards

Use the information in the table below to see how your community water system or well water quality compares to EPA secondary drinking water standards.
Contaminant SMCL (mg/l) Effect(s)
Aluminum 0.05-0.2 Colored water
Chloride 250 Salty taste
Color 15 color units Visible tint
Copper 1.0 Metallic taste; blue-green stain
Corrosivity Noncorrosive Metallic taste; corrosion; fixture staining
Fluoride 2 Tooth discoloration
Foaming agents 0.5 Frothy, cloudy; bitter taste; odor
Iron 0.3 Rusty color; sediment; metallic taste; reddish or orange staining
Manganese 0.05 Black to brown color; black staining; bitter metallic taste
Odor 3 threshold order number "Rotten egg," musty, or chemical smell
pH 6.5-8.5 Low pH: bitter, metallic taste, corrosion;
High pH: slippery feel, soda taste, leaves deposits
Silver 0.10 Skin discoloration; greying of the white part of the eye
Sulfate 250 Salty taste
Total dissolved Solids (TDS) 500 Hardness; deposits; colored water; staining; salty taste
Zinc 5 Metallic taste
Source: EPA, "Water on Tap," July 1997.

The National Secondary Drinking Water Standards (NSDWS) protect the public from odor and aesthetic problems in drinking water that could cause many people to stop using the affected public water system. A Suggested Maximum Contaminant Level (SMCL) for each pollutant are guidelines only. These SMCLs are referred to as the National Secondary Drinking Water Standards (NSDWS). Some of the contaminants listed above do not have established SMCLs because it is not possible to determine their levels in drinking water.The standards for these 15 contaminants are merely advisory, and EPA cannot enforce them.

Note: Individual states may enforce their own drinking water standards as long as they are no less stringent than the NPDWS regulations. Each state may regulate additional contaminants in drinking water or may establish more stringent SMCLs for the contaminants listed in the Table above. For a list of the drinking water contaminants regulated by your state, contact your state agency. EPA has a list on the
Safe Drinking Water Hotline at (800) 426-4791

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