Drinking Water Quality in Idaho

EPA's federal drinking water database lists 765 active community water systems in Idaho as of its April to June 2026 extract, together reporting 1.6 million people served across 44 counties. The largest is Veolia Water Idaho, listed at 264,978 people served. The rest of the population is on smaller community systems, on non community systems such as schools and campgrounds with their own wells, or on private wells, which no federal program regulates. Enter your ZIP in the lookup tool on this page to see the systems EPA lists for your county.

That is a question for your water system and the agencies, not for this site, and here is exactly where the answer lives. Every community water system must publish an annual water quality report: in EPA's words, "EPA requires community water systems to deliver a Consumer Confidence Report, also known as an annual drinking water quality report, to their customers. These reports provide Americans information about their local drinking water quality." Find yours through EPA's Consumer Confidence Report search, ask your utility for the current one, or contact Idaho Department of Environmental Quality, which runs the drinking water program in Idaho. What this page shows is EPA's violation record for each system, which is a compliance history, not a safety verdict in either direction: EPA notes it "is aware of inaccuracies and underreporting of some data in this system."

EPA sorts them into its own categories, and the difference matters. Health based violations are the serious kind: "These violations fall into three categories: Exceedances of the maximum contaminant levels (MCLs), which specify the highest allowable contaminant concentrations in drinking water; Exceedances of the maximum residual disinfectant levels (MRDLs), which specify the highest concentrations of disinfectants allowed in drinking water; and Treatment technique requirements, which specify certain processes intended to reduce the level of a contaminant." Monitoring and reporting violations mean a required test or report did not happen on schedule, which says nothing about what was in the water and everything about whether anyone checked. Most listed violations nationally are in the monitoring and reporting categories. This page shows both, labelled with EPA's categories, never merged into a score of ours.

No, and EPA itself is explicit about why: "However, EPA is aware of underreporting of violations and returns to compliance into SDWIS. EPA cautions users that a list of systems with no violations in ECHO represents the best data we have available, but may not be a true representation of current compliance." A system with nothing listed has NO REPORTED violations in the federal database, which is the best available public record and still not the same thing as a clean bill. The system's own annual Consumer Confidence Report, which tests actual water, is the document to read, and this page links EPA's search for it.

By reported population served, 23 percent of community system customers in Idaho drink surface water (rivers, lakes and reservoirs, including purchased surface water) and 77 percent drink ground water from wells. That ground water majority is nationally unusual: across the country about 72 percent of the served population is on surface water. 16 of the state's 765 systems buy some or all of their water wholesale from another system. Counted from EPA's April to June 2026 SDWA extract.

Idaho Department of Environmental Quality holds primacy, meaning EPA delegated it the day to day running of the federal drinking water program: system inventories, sampling schedules, violations and enforcement. In EPA's words, "The Safe Drinking Water Act (SDWA) gives individual states the opportunity to set and enforce their own drinking water standards if the standards are at a minimum as stringent as EPA’s national standards." The federal database this page reads is what the state reports up to EPA, so the state program's own records are the more detailed and more current place for any single system.

They are outside everything on this page. EPA's words: "The quality and safety of drinking water from private domestic wells are not regulated by the Federal Government under the Safe Drinking Water Act nor by most state governments and laws." And they are common: "Around 15 percent of the U.S. population (over 43 million) rely on private wells as their source of drinking water." If you are on a well, the testing is yours to arrange; Idaho Department of Environmental Quality and your county health department publish what to test for locally, and CDC publishes general well testing guidance. No violation data exists for private wells because nobody is required to report any.

From EPA's quarterly SDWA download, the public extract of the federal Safe Drinking Water Information System (SDWIS), April to June 2026 edition, published July 2026. We kept every active community water system, joined its counties served, and counted its listed violations by EPA's own categories, deduplicating the one row per enforcement action the raw file carries. A US Government work in the public domain. What SDWIS holds is what the states reported to EPA: a system's own test results live in its Consumer Confidence Report, linked for every system above, and private wells are outside the database entirely.