Contaminants and rules in District of Columbia water systems
14 different rules and contaminants appear in the past three years of violation records for District of Columbia's 14 active public water systems. The tables show how many systems each one affected and how many of those violations are still unresolved. Most entries are monitoring, reporting, or notification lapses rather than confirmed contamination.
Microbial
Bacteria and the rules that test for them. Health-based when a sample is positive.
| Rule or contaminant | Code | District of Columbia systems with violations, 3 yr | Share | In violation, latest quarter |
|---|---|---|---|---|
| Revised Total Coliform Rule (RTCR) | 8000 | 4 | 29% | 2 |
| E. coli (Escherichia coli) | 3014 | 1 | 7% | 1 |
Inorganic Chemical
Naturally occurring or from fertilizer and industry. Each has a maximum contaminant level.
Disinfection Byproduct
Formed when chlorine reacts with organic matter in the water.
| Rule or contaminant | Code | District of Columbia systems with violations, 3 yr | Share | In violation, latest quarter |
|---|---|---|---|---|
| TTHM (Total Trihalomethanes) | 2950 | 5 | 36% | 0 |
| Total Haloacetic Acids (HAA5) | 2456 | 4 | 29% | 0 |
Treatment Technique
Rules that require a process, such as corrosion control or disinfection, rather than a measured limit.
| Rule or contaminant | Code | District of Columbia systems with violations, 3 yr | Share | In violation, latest quarter |
|---|---|---|---|---|
| Groundwater Rule (GWR) | 0700 | 7 | 50% | 7 |
| Lead and Copper Rule Revisions (LCRR) | 5200 | 2 | 14% | 2 |
| Chlorine (MRDL) | 0999 | 1 | 7% | 0 |
| Surface Water Treatment Rule (SWTR) | 0200 | 1 | 7% | 0 |
| Long Term 2 Enhanced Surface Water Treatment Rule (LT2) | 0800 | 1 | 7% | 1 |
| Lead and Copper Rule (LCR) | 5000 | 1 | 7% | 1 |
Radionuclide
Naturally occurring radioactive elements in groundwater.
| Rule or contaminant | Code | District of Columbia systems with violations, 3 yr | Share | In violation, latest quarter |
|---|---|---|---|---|
| Gross Alpha, Excl. Radon and U | 4000 | 1 | 7% | 0 |
| Combined Uranium | 4006 | 1 | 7% | 0 |
About this data
A system is counted once per rule if any of its violations in the past three years involved that rule, including monitoring and reporting lapses. In violation, latest quarter counts systems whose contaminant list for the latest official quarter in EPA's data, or new violations reported since, includes this entry. Share is of the 14 active District of Columbia systems.
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 District of Columbia 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.