As of 2026-10-07. Limits come from US EPA and the New York State Department of Health (NYSDOH). Rules change; sources are linked below. Private wells aren't regulated like public water: NYSDOH uses public-water standards as guidelines for private wells.
Positive for total coliform or E. coli? NYSDOH advises you to stop drinking and cooking with the water, use bottled water, and contact your county or local health department. Find yours at health.ny.gov/contact/contact_information/. If anyone has symptoms such as diarrhea or vomiting, contact a health care provider.
What the result means
NYSDOH calls total coliform an "indicator of possible disease-causing contamination." E. coli indicates fecal contamination. In New York, any positive result is above the limit.
Typical next steps
Call your local health department and follow its advice.
Inspect the well cap, casing, and grading for an entry point.
Disinfect (shock-chlorinate) the well following NYSDOH's restoring and testing guidance: health.ny.gov/environmental/water/drinking/restoring_testing_well.htm
Retest at an ELAP-certified lab after disinfection. Sampling errors can cause false results, so follow the lab's bottle instructions exactly.
If it keeps coming back, ask a professional about ongoing disinfection (UV, continuous chlorination).
How often to test
NYSDOH recommends a bacteria test every year, ideally in late spring or early summer, and again after any flood, repair, or disinfection.