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Department of Health Services

Environmental Health

Well Water Quality

Private well water is not regulated by any government agency and it is the responsibility of the individual property owner to ensure that their drinking water supply is safe by having the well water tested by a state certified laboratory. Landlords are required to provide potable water to their tenants.

Using Government Water Standards to Assess Your Private Water Well

Public water systems are regulated by county, state, or federal government, usually depending on the number of connections the water system serves. Public water systems are required to provide to their customers, at least once a year, a notice of water quality.

While many states have adopted the safe drinking water standards of the federal government (United States Environmental Protection Agency-USEPA), the State of California has adopted its own regulatory safe water standards for public water systems that are at least as restrictive as those of the USEPA.

While the standards established for public drinking water systems are not enforceable for private well water, they can provide a parallel indication of the quality and safety of water that comes from private wells. Standards associated with public drinking water supplies are:

  • MCL is the Maximum Contamination Level permissible in public drinking water supplies. MCLs are established based on a number of considerations, including health risk, technological feasibility, treatment costs to water systems, and public hearings.
  • PHG is the Public Health Goal established for public drinking water based on health risk assessment alone and is the level at, or below which, health effects are not expected to occur from a lifetime of exposure.

Click here for well water testing information.

Click here for information on well disinfection.

For more information on drinking water wells and septic systems in Sonoma County please visit the Well and Septic page or contact Permit Sonoma Well and Septic at (707) 565-2849.