Coliform bacteria & E. coli
Also reported as: bacteria, total coliform, E. coli
What it is
Coliforms are bacteria that are common in the environment. Water systems test for them as an indicator: their presence means germs may be able to get into the water. E. coli is a specific type that indicates fecal contamination.
Your body
According to EPA, germs indicated by E. coli can cause stomach cramps, diarrhea, nausea, and headaches, and may pose a special risk for infants, young children, and people with severely compromised immune systems.
Your home
Bacteria do not damage plumbing, but in wells they can point to a cracked well cap, a damaged casing, or nearby septic issues.
Federal standard: Treatment technique; E. coli MCL (EPA Revised Total Coliform Rule)
Treatment options that can reduce it
UV disinfection works best with sediment pre-filtration in front of it, and the well should also be inspected.
Research & sources (3)
Maryland water systems that reported coliform bacteria & e. coli
- Baltimore City Department of Public WorksBaltimore City (also serves most of Baltimore County) · 2025 data
- City of FrederickFrederick · 2025 data
- Harford County Department of Public WorksHarford · 2025 data
- WSSC WaterMontgomery and Prince George's · 2025 data
See common private-well contaminants →
The information on this site is for general education only and is not medical advice. Talk with a qualified health professional about health concerns. Water treatment equipment performance depends on the system, its certification, and proper maintenance.
Find out what's in your water. It's free.
Book a free in-home water test, or call and talk to a real person in Easton.