Coliphage in drinking water
227 active public water systems in 2 states had a Coliphage violation in the past three years, and 5 had one in the latest quarter of EPA's data.
You are on Tapcensus, an independent guide to the EPA compliance records of every public water system in the United States. This page explains Coliphage and lists the water systems whose records include a related violation. It does not show measured levels.
Is Coliphage in the records for your water system?
Enter a ZIP code, town, or street address to see the water systems that serve your area, their status, and which rules and contaminants appear in their violations.
Enter a ZIP code, town, or street address.
The standard and what a violation means
Water systems with a Coliphage violation, by state
Active public water systems that reported at least one related violation to EPA in the past three years. Each state links to the list of its affected systems.
| State | Systems with violations, 3 yr | Share of active systems | In violation, latest quarter |
|---|---|---|---|
| Oregon | 224 | 9% | 4 |
| California | 3 | 0% | 1 |
Largest water systems with a Coliphage violation
The ten biggest systems, by people served, whose records include a related violation in the past three years.
| System | Serves | Status | Rules violated, 3 yr | Unresolved |
|---|---|---|---|---|
|
Milwaukie, City of Clackamas County |
20,946 | 6 | 1 | |
|
Troutdale, City of Multnomah County |
16,185 | 1 | 0 | |
|
Cornelius, City of Washington County |
14,490 | 2 | 0 | |
|
Prineville, City of Crook County |
11,000 | 5 | 1 | |
|
Sheridan, City of Yamhill County |
6,494 | 7 | 0 | |
|
Boardman, City of Morrow County |
5,749 | 3 | 1 | |
|
Aumsville, City of Marion County |
4,125 | 2 | 0 | |
|
Mount Angel, City of Marion County |
3,650 | 3 | 0 | |
|
Hubbard, City of Marion County |
3,478 | 1 | 0 | |
|
Lakeview, Town of Lake County |
2,476 | 10 | 2 |
About this data
A system is counted once if any of its violations in the past three years involved Coliphage, including monitoring and reporting lapses. Rules violated and status in the systems table are for the whole system, not Coliphage alone. Counts cover active systems in all 50 states and the District of Columbia.
Source: the U.S. EPA's Enforcement and Compliance History Online system (ECHO), which publishes the federal Safe Drinking Water Information System. EPA's terms and values are shown as published. The records are from EPA's data refresh of Oct 7, 2026; EPA refreshes this data quarterly, and states report to EPA with a lag of three to six months, so the newest violations may not appear yet.