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.
If your report shows coliform or E. coli "present," or any result above a limit, NYSDOH advises you to stop drinking the water, use bottled water, and contact your county or local health department (find yours). Use a NYSDOH ELAP-certified lab for testing and retesting.
Units: the #1 source of confusion
You see
Means
Same as
mg/L
milligrams per liter
ppm
µg/L (ug/L)
0.001 mg/L
ppb
ng/L
0.000001 mg/L
ppt (used for PFAS)
pCi/L
picocuries per liter
radioactivity (radon, radium)
Example: arsenic's limit is 0.010 mg/L, the same as 10 µg/L (10 ppb).
Common report terms
ND or "<": not detected above the lab's reporting limit. It means "not found above what this test can see," not zero.
Present / Absent: used for total coliform and E. coli. NYSDOH treats any positive as above the limit.
MCL: the enforceable limit for public water systems. SMCL: a non-enforceable guideline for taste, staining, or scale. Action level: a treatment trigger for lead and copper, not an MCL.
"Exceeds" flags: the lab compared you to its own reference list. Check which standard it used.
Where New York differs from federal limits
Test
Federal (EPA)
New York (NYSDOH)
Manganese
SMCL 0.05 mg/L; health advisory 0.3
MCL 0.3 mg/L; iron + manganese ≤ 0.5
Iron
SMCL 0.3 mg/L
MCL 0.3 mg/L
Fluoride
MCL 4.0 mg/L
MCL 2.2 mg/L
PFOA / PFOS
MCL 4.0 ng/L each (2024 rule; public-system compliance by 2029)
MCL 10 ng/L each
1,4-Dioxane
No federal MCL
MCL 1 µg/L
The full guide covers about two dozen tests with urgency labels, matching treatment types, and published cost ranges.