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Understanding Your Drinking Water Test Results

Bacteriological analysis of water is for total coliform. There are four methods which may be used by laboratories for the analysis of drinking water for total coliform.  

Depending on the method used, the sample analysis could be completed within 24 to 96 hours. These coliform organisms are common inhabitants of the intestinal tracts of humans and other warm blooded animals.

They can be found in topsoil, sewage, ponds, lakes, and other surface waters. The presence of these organisms in your water supply may mean that your drinking water is not properly protected from contamination, which may include human disease causing organisms. Coliform organisms themselves usually will not cause disease.

Results of Analysis - Coliform

Not Detected - No coliform organisms were detected in the water sample. The sample meets the state drinking water standard for bacteriological quality at the time of sampling. (Similar results may be reported as negative, absent, or zero, "0".) 

Positive - Coliform organisms were present in the water sample. Safety can't be assured. Collection of a resample to confirm the original result is recommended. An investigation into the cause of the problem by a qualified individual is advised. (Similar results may be reported as present or any number from 1 to 200.)

Fecal Coliform Detected - Fecal coliform organisms were detected in the water sample. Fecal organisms are found in the intestines of warm blooded animals, and, as such, their presence in a water supply is considered an indication of sewage contamination. Precautions are recommended in the use of the water supply.

Sample more than 30 hours old when received at the laboratory - Coliform organisms may die between sample collection and testing, or other bacteria may grow causing interference. If the time between sample collection and testing exceeds the above time limits, test results should not be considered accurate, and a check sample is recommended

Partial Chemical Analysis

The Michigan Department of Public Health laboratory analyzes drinking water for eight parameters in a routine testing procedure referred to as a partial chemical analysis. Below is a table of these parameters and associated problems.  Except for fluoride and nitrate, the levels listed below are general guidelines. State drinking water standards have been established and are listed for these two chemicals.

Test Excellent Satisfactory Objectionable Problem
Iron 0-0.2 0.2-0.5 Over 0.5 Staining, turbidity taste, odor
Sodium 0-20 20-160 Over 160 Taste, special diets may require water of low sodium content
Nitrate (NO3) 0 1-10 Over 10 (State drinking water standard is 10) Nitrate poisoning-especially infaNitrate/td>
Nitrite 0 0-1 Over 1 Nitrite poisoning-especially infants
Hardness (CaCo3) 25-100 100-250 Over 250 or less than 25 Scaling of water fixtures, soap scum at high levels; corrosion at low levels
Sulfate 0-50 50-250 Over 250 Laxative effect, odor, scaling in boilers, heat exchangers
Chloride 0-20 20-250 Over 250 Taste; corrosion



0.7-2.0 or 1.7-2.4

Over 4.0 (State drinking water standard is 4)

Low levels are beneficial in preventing tooth decay. High levels may cause mottling of teeth


Test results are reported in milligrams per liter (mg/l) for all parameters.

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