Iron and Manganese
Reddish-brown staining points to iron; black or dark gray staining points to manganese. They require different treatment.
Short answer: Iron typically causes reddish-brown staining; manganese typically causes black or dark gray staining. Both are common in Delaware groundwater and are generally aesthetic (nuisance) issues addressed through targeted filtration once confirmed by testing.
Common signs
- Iron: reddish-brown staining on fixtures, laundry, and toilet tanks; metallic taste.
- Manganese: black or dark gray staining; sometimes a similar metallic taste.
- Sediment buildup in aerators, water heaters, and appliances from either.
Step-by-step
- Test to confirm iron and/or manganese levels rather than assuming from staining color alone.
- If you're on a private well, use Delaware DPH-connected resources or a certified laboratory.
- Choose treatment (oxidation/filtration media suited to the specific metal and level) matched to your test result.
- Maintain the treatment system on the manufacturer's schedule and retest periodically.
Common mistakes
- Assuming staining color alone confirms iron versus manganese without testing
- Using an iron-only filtration media that doesn't effectively remove manganese
- Buying treatment before understanding whether the source is your plumbing or your water supply
Official sources
- U.S. EPA secondary drinking-water standards
- Delaware Public Health Laboratory and certified laboratories
Related
Are iron and manganese a health risk?
For most households, both are treated as aesthetic (nuisance) concerns rather than acute health risks, though very high manganese levels have been studied for other effects. Test to know your specific levels.
Does not endorse a specific manufacturer or product claim.
Last reviewed: 2026-07-11. Report a correction.