Drinking water quality is monitored by public drinking water systems, and data are reported to the State Water Resources Control Board (SWCRB). Drinking water standards are limitations on how much of a given contaminant is allowed in drinking water. These limits, known as maximum contaminant levels (MCLs), are set at levels necessary to protect the public from acute and chronic health risks associated with consuming contaminants in drinking water.
Drinking water standards and monitoring requirements are set by federal and state laws. Water systems must establish drinking water monitoring plans that follow the sampling, testing, and reporting requirements set by the US Environmental Protection Agency (EPA) and the Safe Drinking Water Act (SDWA).
The location of sampling points within a water system, the frequency of sampling, and the reporting of test results vary based on the contaminant, the size of the population served by the water system, past monitoring results, the type of source water, and other factors. State water agencies like the SWRCB specify sampling locations and acceptable analytical methods.
State-level drinking water standards can be found in Title 22 of the California Code of Regulations. All of the contaminants we provide data for have primary MCLs, which address health concerns. When it is not feasible to measure a contaminant in drinking water, the EPA does not set MCLs and instead establishes drinking water Treatment Technique Requirements (TTR). The TTRs set standards about the type of treatment required and about measuring how well these treatment processes are working.