Water Testing and Interpretation: The Secondary Drinking Water Standards¹

Judith C. Stewart, Ann T. Lemley, Sharon I. Hogan, Richard A. Weismiller, and Arthur G. Hornsby ²

Water testing is usually the first approach to dealing with water quality problems. An analysis of your water not only will confirm what you may already know-that your water has an odor, deposits scale, stains plumbing, is colored or frothy, or corrodes-but also will help you determine the extent of your problem and the best way to solve it.

Drinking Water Standards

A laboratory analysis of water identifies the concentration of certain contaminants, usually in milligrams per liter (mg/L). Other units of measurement are used for several physical characteristics, depending on the analytical method. A good way to interpret a water test is to compare the reported concentrations with government standards.

These standards are established by the U.S. Environtal Protection Agency (EPA) to limit contaminant concentrations to acceptable levels. Drinking water contaminants that affect the safety of drinking water and may cause health problems are regulated by Primary Drinking Water Standards. Primary Standards are enforced by the Federal government. These standards only apply to public drinking water systems, but, they also serve as a guide to water quality for individual water supplies.

Secondary Drinking Water Standards, also known as Secondary Maximum Contaminant Levels (SMCLs), are concentration limits for nuisance contaminants and physical problems. Secondary Standards are not enforced by state and federal governments, and municipal water systems are not required to test for and remove secondary contaminants. However, they are useful guidelines for water suppliers and well owners who wish to ensure that their water will be suitable for all household uses, including drinking, bathing, washing and cooking.

Testing For Secondary Contaminants

Table 1 is a guide to testing for water quality problems caused by secondary contaminants. A water analysis identifying levels of a contaminant significantly greater than its SMCL indicates that you may need to treat your water. Your decision on whether or not to treat your water will largely be based on personal preference. The contaminant level and possible source of contamination are important data as you consider home treatment and alternative remedies such as bottled water.

Physical Problems That Effect drinking Water

Table 2 presents symptoms and tests for determining the causes of various physical problems.

Water Hardness

Water hardness does not have a Secondary Maximum Contaminant Level. It is included here, however, because it is a common water quality problem and testing for water hardness is frequently necessary to evaluate and treat other problems.

The source is naturally dissolved calcium and magnesium from soil and lime The symptoms are soap deposits; scaly deposits in plumbing and appliances; and decreased cleaning action of soaps and detergents. Test for classification of water hardness using the following concentrations of hardness minerals in grains per gallon (gpg) :

below 1.0 gpg = soft
1. 0 to 3.5 gpg = slightly hard
3.5 to 7.5 gpg = moderately hard
7.5 to 10.5 gpg = hard
10.5 and above = very hard

Tables

Table 1.

Tests for inorganic contaminants.

Contaminant	Source	Symptoms	Test	SMCL
Aluminum				0.05-0.02 mg/L
Chloride	natural minerals; seawater; road salt; fertilizers; industrial wastes and sewage.	salty tastes; corroded pipes, fixtures and appliances; blackening and pitting of stainless steel.	chloride	250 mg/L
Copper	leaching from copper water pipes and tubing; industrial and mining wastes.	bitter or metallic taste; blue-green stains on plumbing fixtures.	copper	1.0 mg/L
Fluoride	natural minerals and industrial wastes.	brownish discoloration of teeth.	fluoride	2.0 mg/L
Iron	natural deposits in rocks and soil; leaching of cast iron pipes in water distribution systems.	brackish color; rusty sediment; bitter metallic taste; brown-orange stains; iron bacteria and discolored beverages.	iron	0.3 mg/L
Manganese	natural deposits in rocks and soil	brownish color; black stains on laundry and fixtures; bitter taste; altered taste of water-mixed beverages.	manganese	0.05 mg/L
Silver	soil, coal, and mineral deposits; ore mining and manufacture of alloys; photographic procedures and jewelry making.	agryia, a permanent blue-gray discoloration of skin, mucous membranes and eyes.	silver	0.10 mg/L
Sulfate	natural deposits or salts; byproducts of coal mining; industrial wastes and sewage.	bitter medicinal taste; scaly deposits; corrosion; laxative effects; "rotten egg" odor from hydrogen sulfide gas formation.	sulfate	250 mg/L
Total Dissolved Solids (TDS)	dissolved minerals; iron and manganese.	hardness, scaly deposits; sediment; cloudy, colored water; odor; staining; salty or bitter taste.	electrical conductivity	500 mg/L
Zinc	natural deposits; leaching of galvanized pipes and fittings.	metallic taste.	zinc	5 mg/L

Table 2.

Physical problems of water contamination

Contaminant	Source	Symptoms	Test	SMCL
Color	iron, copper, or manganese; organic chemicals; organic matter.	visible tint	color	15 color units
Corrosivity	depends on temperature, acidity, hardness, and oxygen content of water.	pitted or leaking pipes; metallic taste; staining due to lead, copper, iron, of zinc dissolved from plumbing.	corrosion index	noncorrosive
Detergents/foaming gents	household and industrial wastes.	frothy, cloudy appearance; soapy taste and unpleasant odor.	methylene blue test	0.5 mg/L
Odor	dissolved gases, minerals, chemicals; leaking underground storage tanks; landfill or septic runoff; organic matter.	"rotten egg", septic, musty or chemical smell.	odor	3 Threshold Odor Number (TON)
pH	dissolved acid and alkaline materials	pitting of pipes and fixtures, biter or metallic taste (low pH); slippery feel, soda taste, scaly deposits (high pH.)	pH	6.5 to 8.5 on pH scale

Footnotes

This document is SL160, a series of the Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published February 2001. Please visit the EDIS Web site at http://edis.ifas.ufl.edu.

Judith C. Stewart, Extension support aide, Ann T. Lemley, Associate Professor, College of Human Ecology, Cornell University, Sharon I. Hogan, communications consultant, and Richard A. Weismiller, soil and water resource specialist, Department of Agronomy, University of Maryland., Arthur G. Hornsby...()()().., Professor, Soil and Water Science Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611. Originally written and produced in 1988, revised 1988-89, by Cornell University and the University of Maryland under the sponsorship of the USDA Extension Service.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer, Interim Dean.

Water Testing and Interpretation: The Secondary Drinking Water Standards1