Uranium in well water: limits and what to do
The EPA limit is 30 µg/L and Ontario's is 20 µg/L. Above it, long term drinking can affect the kidneys. Reverse osmosis and anion exchange remove it.
- US (EPA)
- 30 µg/L (0.030 mg/L).
- Ontario
- 20 µg/L (0.020 mg/L).
What it is
Uranium occurs naturally in some granite and other bedrock. The concern in drinking water is mostly chemical, its effect on the kidneys over many years, rather than radiation.
What your number means
- Within limitsBelow half the limit
Under the limit. Retest every few years.
- Worth a lookHalf the limit to the limit
Under the limit but worth watching. Retest within a year.
- Act nowAbove the limit
Use another source for drinking and cooking and look at treatment.
What to do
- Use another source for drinking and cooking if you're over the limit.
- Retest to confirm.
- Ask about reverse osmosis or anion exchange treatment certified for uranium.
- Ask your lab about radon in water too, since both come from similar rock.
How often to test
Every 3 to 5 years, or within a year if close to the limit.
Common questions
Is uranium in water radioactive?
Slightly, but at drinking water levels the main concern is chemical damage to the kidneys over time.
My lab reported pCi/L. Is that the same?
No. pCi/L measures radioactivity. Limits for uranium are usually set in µg/L, so compare that number.
Sources: EPA drinking water standards; Ontario Drinking Water Quality Standards, O. Reg. 169/03. Limits checked October 2026.