How Often Is My Water Supply Tested?
To find out how frequently your drinking water is tested, contact your water system or government agency in charge of drinking water.
The table on this page shows the major groups of
contaminants and the minimum frequency that public water systems
must test for them. If a problem is detected, there are immediate
retesting requirements that go into effect and strict
instructions for how the system informs the public about the
problem. Until the system can reliably demonstrate that it is
free of problems, the retesting is continued.
| Sample Monitoring Schedule | |
| Contaminant | Minimum Monitoring Frequency |
| Acute Contaminants | |
| Bacteria | Monthly or quarterly, depending on system size and type |
| Protozoa and Viruses | Continuous monitoring for turbidity, monthly for total coliforms, as indicators |
| Nitrate | Annually |
| Chronic Contaminants | |
| Volatile
Organics (e.g., benzene) |
Ground water systems, annually for 2 consecutive years; surface water systems, annually |
| Synthetic
Organics (e.g., pesticides) |
Larger systems, twice in 3 years; smaller systems, once in 3 years |
| Inorganics/Metals | Ground water systems, once every 3 years; surface water systems, annually |
| Lead and Copper | Annually |
| Radionuclides | Once every 4 years |
| General requirements may differ slightly based on the size or type of drinking water system. | |
Although failure to monitor does not necessarily suggest safety problems, conducting the required monitoring and reporting is critical to ensure that problems will be detected. Consumers can help make certain monitoring and reporting requirements are met by first contacting their drinking water agency to determine if their water supplier is meeting all requirements. If the water supplier is not meeting the requirements, consumers can work with local officials and their water supplier to ensure that the required monitoring gets done.
Adapted From:
EPA 815-K-97-002
Water On Tap
July 1997
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