Typically water supply networks deliver a single quality of water, whether it is to be used for drinking, washing or landscape irrigation; one counterexample is urban China, where drinking water can be optionally delivered by a separate tap. In the United States, public drinking water is governed by the Safe Drinking Water Act (SDWA).
The standard test for bacterial contamination is a laboratory analysis of coliform bacteria, a convenient marker for a class of harmful fecal pathogens. The presence of fecal coliforms (like Escherichia coli) serves as an indication of contamination by sewage.
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