What is a Water Purity Test?


A water purity test is performed by a State Certified Laboratory to detect the presence of a cateria and pathogenic (disease-causing) organisms.

The EPA has designated Total Coliform bacteria as a standard to determine the bacterial safety of water. Total coliforms are a group of closely related bacteria that are (with few exceptions) not harmful to humans. Because total coliforms are common inhabitants of ambient water and may be injured by environmental stresses (e.g., lack of nutrients) and water treatment (e.g., chlorine disinfections) in a manner similar to most bacterial pathogens and many viral enteric pathogens, the EPA considers them a useful indicator of these pathogens. More importantly, for drinking water, total coliforms are used to determine the adequacy of water treatment and the integrity of the distribution system. The absence of total coliforms in the distribution system minimizes the likelihood that fecal pathogens (Ecoli) are present. Thus, total coliforms are used to determine the vulnerability of a system to fecal contamination.

The TCR requires systems to monitor for total coliforms at a frequency proportional to the number of people served. If any sample tests positive for total coliforms, the system must perform the following additional test:

  • Further test that culture for the presence of either fecal coliforms of Escherichia coli.


What to do if your Water Purity test fails to meet New York State standards for drinking water


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