After the consumer has sent a water sample to a lab, the lab will return a report similar to the one shown (click on the picture to the left to see a larger version). It will contain a list of the contaminants tested, the concentrations, and in some cases, highlight any problem contaminants.
An important feature of the report is the units used to measure the contaminant level in the water. Milligrams per liter (mg/l) of water is typically used for substances like metals and nitrates. A milligram per liter is also equal to one part per million (ppm). About 0.03 of a teaspoon of sugar dissoved in a bathrub of water is an approximation of one ppm. For toxic substances and some other concentrations, the units used are even smaller. In these cases, parts per billion (ppb) are used. Another unit found on some test reports is that used to measure radon-picocurries per liter. Some values like pH, hardness, conductance, and turbidity are reported in units specific to the test.
In addition ot the test results, a lab may make notes on any contaminants that exceeded the USEPA or State drinking water standards. For example, in the sample shown, the lab noted that total coliform bacteria and iron both exceeded the standards. Sometimes the lab will send additional information about the health effects or treatment options for problem contaminants.
Retain your copy of the report as a record of the quality of the water supply. If potential polluting activities occur in the area, a record of past water quality may be needed in order to prove that water quality has changed. Records of water quality are also important for land transfer purposes.
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