Antimony in well water: limits and sources
The limit for antimony is 0.006 mg/L (6 µg/L) in both the US and Ontario. It is rarely found in wells. Long term exposure above the limit can raise blood cholesterol and lower blood sugar.
- US (EPA)
- 0.006 mg/L.
- Ontario
- 0.006 mg/L.
What it is
Antimony can come from some plumbing solder and fittings, from mining areas, or from industrial sources. Natural levels in groundwater are usually very low.
What your number means
- Within limitsBelow 0.003 mg/L
Under the limit by a comfortable margin.
- Close to limit0.003 to 0.006 mg/L
Under the limit but more than halfway there. Retest within a year.
- Above limitAbove 0.006 mg/L
Use another source for drinking and cooking, contact your health department and retest to confirm.
What to do
- Retest to confirm, and flush the tap before sampling to rule out plumbing.
- Above the limit, use another source for drinking.
- Reverse osmosis removes antimony.
How often to test
With a full panel every 3 to 5 years.
Common questions
Can plumbing add antimony?
Some older solders and fittings contain antimony. A first draw sample and a flushed sample can show whether it comes from plumbing.
Is antimony common in wells?
No. Most results come back below detection.
Sources: EPA drinking water regulations; Ontario Drinking Water Quality Standards (O. Reg. 169/03). Limits checked November 2026.