Interpreting Drinking Water Test Results

1 Interpreting Drinking Water Test Resultsby Chris Mechenich and Elaine AndrewsRotten-egg smells, red-brown stains on plumbing fixtures,bathtub rings all these are unpleasant signs of Water qualityproblems, but usually not of harmful contaminants in thewater. Contaminants that may threaten our health are usually notdiscernible by the senses. Drinking Water can contain nitrate,bacteria, and pesticides at levels which cannot be tasted or smelled,but which can be hazardous to your Drinking Water comes from a private well, you should testyour Water once a year even if you do not observe any smells, stainsor changes in Water quality.

2 Only analysis by a certified laboratorycan determine if the Water is free of harmful contaminants. Thispublication provides information about how to interpret thelaboratory Results for a basic set of tests that are recommended for allprivate tests described in this publication are also conducted on publicwater supplies. If you are using Water from a public Water utility,consider having the Water tested if your home plumbing systemcontains lead pipes or lead solder, if you are installing a watertreatment device, or if you have concerns about the Water . See factsheet G3558-3 Evaluating the Condition of Your Public Water Supply,for more Initial Set of Water TestsAnyone buying a new home with a private well, installing a newwell or simply having their well Water tested for the first time shouldrun the basic set of tests described here.

3 These tests give a goodoverall picture of current Water quality, indicate possible problems,and provide a baseline for comparing future test Results . Each testis described in more detail in this have a certified laboratory conduct the certified bythe Department of Natural Resources must meet standards foraccuracy and quality. A list of certified labs is available from countyExtension offices and district Department of Natural Resources(DNR) offices. This fact sheet is part of a seriesdesigned to help you determinethe quality of your home drinkingwater and to show you techniquesavailable for improving it.

4 Tomake the best use of thesepublications, include them in ahousehold file containing wellinformation and Water test Results . Other fact sheets in the series are:G3558-1 Keeping YourHome Water Supply SafeG3558-2 Evaluating theCondition of Your PrivateWater SupplyG3558-3 Evaluating theCondition of Your PublicWater SupplyG3558-5 Choosing a WaterTreatment DeviceExtension bulletin G3399 Maintaining Your Home Well WaterSystem, can be used with thesepublications. This series was developed by theUniversity of WisconsinCooperative Extension incooperation with the WisconsinDepartment of Natural Resourcesand the Wisconsin Department ofIndustry, Labor and to Identify Contaminants that Harm bacteria are usually not harmful, but indicatethe possible presence of disease-causing bacteria from human oranimal form of nitrogen that can dangerously reduce theamount of oxygen in the blood of infants under six months , introduced into groundwater by humans, is a commoncontaminant.

5 And often indicates the presence of can be leached into Water from lead pipes or solder andcan represent a significant health to Determine Overall Water QualityALKALINITY. Measurement needed to determine concentrations often indicate contamination by aseptic system, fertilizer, a landfill or road Measures the ability of Water to conduct anelectrical current; can be used to signal the presence combination of several tests that indicatesthe tendency for Water to corrode plumbing, or for lime deposits toform in Helps determine the need for Water softening; alsoinfluences Water 's acidity and helps determine if Water willcorrode plumbing.

6 After running the initial set of tests, well users should continue totest for bacteria once a year. It s also a good idea to test for nitrateannually for several years. If nitrate levels are consistently low,nitrate tests are not necessary every year. However, a nitrate testshould always be conducted if an infant is Drinking the Note on Drinking Water StandardsPublic Water supplies must meet numerical Water quality standardsset by state and federal governments and enforced by the WisconsinDNR. Water from private wells does not have to meet thesestandards. However, users of private well Water should at least beaware of the broad range of contaminants that may be found in wellwater and that concern public health standards provide health limits for 60 contaminants as ofJanuary, 1991.

7 The list continues to grow and may include up to 85contaminants by 1993. It includes 8 inorganic compounds, such asarsenic, copper and lead; 17 pesticides, such as aldicarb andchlordane; 10 volatile organic chemicals such as benzene andtrichloroethylene; PCBs; 3 microbial pathogens; and 5 radioactive2 WHAT IS APARTPERMILLION?Laboratory equipment canmeasure contaminants in Water atextremely low levels, such asparts per million (ppm) or evenparts per billion (ppb). Forexample, one part per millioncan be imagined as one redmarble mixed in with 999,999blue marbles, one inch in sixteenmiles, or a minute in the space oftwo years.

8 One part perbillionis the same as two croutons in afive hundred pound salad, or eightdrops of Water in an Olympic-sized swimming small numbers may seemquite insignificant, even one partper billion or less of certainchemicals has been found tocause adverse health creative part-per-million and part-per-billion examples are from theWaterTest Corporation, New London, NH. elements. Secondary standards provide aesthetic limits for 13contaminants, such as iron, zinc, color and odor. The sources andmaximum contaminant levels (MCL) for these substances aredescribed in the publication Private Drinking Water Supplies listed inthe resource section of this fact private well Water supplies for all these contaminants wouldbe expensive and is not recommended unless your well is too closeto a known source of contamination.

9 The Initial Water Tests:What the Results MeanThe initial set of Water tests can provide a good overview of yourwell Water quality if you know how to interpret the Results . Theinformation below provides a starting point for evaluating yourwater quality. Note that Water test Results are usually presented in milligrams perliter (mg/1) or micrograms per liter ( g/l). For example, a Water testmight indicate that the Water contains 6 mg/l nitrate, meaning thata liter of Water contains an average concentration of 6 milligrams ofnitrate. Note also that one mg/l is equivalent to one part permillion (ppm).

10 One g/l equals one part per billion (ppb).Coliform BacteriaColiform bacteria are microorganisms found in surface Water , soiland in the feces of humans and animals. They do not usually causedisease. However, their presence indicates that wastes may becontaminating the Water and means that pathogenic (disease-causing) organisms could be present. If human or animal wastes arecontaminating the Water , gastrointestinal diseases or hepatitis mayresult. ACCEPTABLE Results :0 coliform/100 milliliters (ml) of Water (alsocalled 0/5). If you have 1 or more coliform colonies/100 millilitersof Water , you should resample.