Water Sampling Requirements
Although groundwater is typically a safe source of drinking water and actual events of drinking water contamination are rare, contaminants can enter the drinking water supply if any of the protective barriers are breeched. Heightened public awareness, concern for public health, and advancements of technology are factors behind legislative action to set national standards regarding the levels of contaminants in drinking water.
Water quality monitoring has an important role in identifying breeches in the system that may threaten safe and aesthetically pleasing water, however, it is important to understand that a water sample is a very small part of the total water supply and not a protective barrier.
There are potentially thousands of different contaminants that could find their way into drinking water systems that may be harmful to health. It is impractical to attempt to test for all possible contaminants. Priorities for testing are determined, in general, based on national occurrence data, health effects and technology.
Sampling requirements are tied to population served, source of water, and results of the sanitary survey.
Total Coliform Monitoring
Systems that serve 1,000 or fewer persons per day must sample quarterly unless on a reduced frequency as prescribed by the local health department.
Systems that serve 1,001 or more persons per day must sample monthly. The number of samples per month is determined by the population served.
Beginning April 1, 2016 the Revised Total Coliform Rule is in effect. For more information about the rule visit our Revised Total Coliform Rule website.
Annual sampling required for all systems unless results indicate a heightened level and increased monitoring in prescribed by the local health department.
Chemical Monitoring for Nontransient Systems
Each system is evaluated and put on a monitoring cycle prescribed by the local health department.
These factsheets describe how to collect a drinking water sample:
DEQ Laboratory Codes