pH in well water: why low pH matters
The recommended range is 6.5 to 8.5. pH itself isn't a health risk, but water below 6.5 is corrosive and can pull lead and copper out of your plumbing.
- US (EPA)
- 6.5 to 8.5, a cosmetic guideline.
- Ontario
- 6.5 to 8.5 operational guideline.
What it is
pH measures how acidic or alkaline water is. Rainwater and some groundwater are naturally acidic. Low pH water corrodes copper pipes, leaving blue green stains and sometimes lead in the water; high pH can taste bitter and leave scale.
What your number means
- Worth a lookBelow 6.5
Acidic and corrosive. Test for lead and copper.
- Within limits6.5 to 8.5
In the normal range.
- Worth a lookAbove 8.5
Alkaline. Bitter taste and scale; makes chlorine disinfection less effective.
What to do
- If pH is low, test for lead and copper at the kitchen tap.
- Ask about a neutralizing (calcite) filter to raise pH.
- Mention high pH if you ever shock chlorinate the well, since it weakens chlorine.
How often to test
With a full panel every 3 to 5 years.
Common questions
What causes blue green stains in my sink?
Usually copper dissolving from pipes because the water is acidic.
Is acidic well water safe to drink?
The acidity itself isn't the problem; the metals it picks up from plumbing can be. Test lead and copper.
Sources: EPA secondary standards; Ontario: testing and treating private wells. Limits checked October 2026.