Water Education Foundation

California Water

Private Wells

When water is provided by a private well, periodic testing of its water is recommended but not mandated. Owners of private wells should use only laboratories certified by the California Department of Heath Services to conduct an analysis. Private wells fall outside federal and state regulation because they are on private land and not covered by the SDWA. They also are not subject to the same periodic testing and monitoring requirements as public water systems. There are more than 600,000 private wells in California.

Experts recommend having private well water tested at least once a year for coliform bacteria.
Experts recommend having private well water tested at least once a year for coliform bacteria. Shallow wells along rivers and wells built without proper sanitary seals are especially susceptible to bacterial contamination from surface water entry.

When it comes to toxic substances, more detailed - and expensive - testing can be done. Testing for minerals can cost from $130 to $200. Testing for organic "priority pollutants" may cost an additional $200 to $300. Testing for all regulated chemicals require even more extensive tests and can cost several thousand dollars per sample. If a contaminant is detected, the results will include the concentration of the contaminant and an indication of whether this concentration exceeds a drinking water quality standard. If a standard is exceeded, consumers are advised to retest the water supply immediately and contact the public health department for assistance.

Sometimes it is not necessary to check for the full range of pollutants. The health department probably is aware of metals or other possible contaminants of concern in the vicinity. County and state health departments keep records on well trouble spots and can advise whether any substances of concern have been found in other area wells nearby. However, water experts caution that different wells may not be drilled to the same depth or obtain water from the same geologic formation.

Information on well water quality is also available from the State Water Resources Control Board. The Groundwater Ambient Monitoring and Assessment (GAMA) Domestic Well Project samples private domestic wells for chemicals commonly found in well water. The areas sampled are chosen based upon existing knowledge of water quality and land use, in coordination with county environmental health agencies. The state incurs the costs of sampling, and the test results are provided to well owners who volunteered to have their well sampled. More information about the GAMA Domestic Well Project is available at http://www.waterboards.ca.gov/water_issues/programs/gama/domestic_well.shtml

In addition, the GAMA website also provides detailed information to private domestic well owners with concerns about their well water quality. The webpage to help you find important information about domestic wells is available at http://www.waterboards.ca.gov/gama/wq_privatewells.shtml

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