When a well water test comes back with elevated iron and manganese together, sizing the filter for just one of them is the most common mistake homeowners make. The two minerals need different oxidation strength to remove, and a system sized only for iron will consistently underperform on manganese, even after the iron problem is gone.
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Sizing Calculator: Iron and Manganese Filter
Based on standard water treatment industry sizing practice for combined iron and manganese oxidizing filters. Always confirm with a certified lab test before buying equipment; this is a starting estimate, not a substitute for a system designed to your actual test results.
In this guide
Why Combined Iron and Manganese Needs Different Sizing
Iron converts to a filterable form at a lower oxidation potential than manganese needs. A media bed sized and rated only for iron will often let manganese pass through, particularly once levels climb past 1 mg/L. The correct approach when a test shows both is to size and select media for whichever contaminant needs the higher oxidation potential, which in practice almost always means sizing for manganese, not for whichever of the two has the larger raw number on the test report.
Manganese greensand, regenerated with potassium permanganate, is the media most consistently recommended for combined iron and manganese because it handles both reliably at moderate-to-high concentrations. Straight air injection oxidation (AIO) systems work fine for iron alone or for low manganese, but need a higher-capacity design once manganese is a meaningful share of the test result.
(Iron + Manganese)
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Media Options Compared
| Combined Level | Recommended Media | Notes |
|---|---|---|
| Under 3 mg/L combined | Air injection oxidation (AIO) | No chemicals needed; fine if manganese is the smaller share of the combined total |
| 3 to 10 mg/L combined | Manganese greensand | Regenerates with potassium permanganate; the standard choice once manganese is a meaningful share |
| Over 10 mg/L, or iron bacteria present | Chemical feed with oxidizer | Chlorine or hydrogen peroxide feed ahead of a retention tank and filter; more maintenance but the only approach that holds up at this level |
When to Call a Pro vs. DIY
A straightforward AIO system for moderate combined levels is a reasonable DIY install for someone comfortable with basic plumbing. If you want to compare iron filter systems side by side before choosing media, start there. Once manganese greensand or a chemical feed system is involved, professional installation is worth the cost: greensand regeneration needs to be programmed correctly for the specific water chemistry, and a chemical feed system sized wrong can either underdose (no improvement) or overdose (chlorine taste and corrosion risk). Get a water treatment professional to size the system against your actual lab results, not just this page’s ranges.