An iron filter for well water is chosen from two numbers and one observation: how much iron the test found, what the pH is, and whether the water is clear when drawn and turns orange later or arrives orange already. Those tell you whether the iron is dissolved or already oxidized, and that single distinction rules out most of the equipment on the market.
Clear water iron and red water iron
Water that comes out clear and turns rust-colored in a glass after a few minutes carries dissolved iron, which is invisible until it meets air. Water that is orange the moment it leaves the tap carries iron that has already oxidized into particles. Dissolved iron can be exchanged out or oxidized deliberately and then filtered. Particulate iron has to be filtered mechanically. Do the glass test yourself before believing any recommendation.
Where a softener is enough, and where it is not
Penn State Extension notes that a softener can remove dissolved iron when the pH is above 6.7, hardness sits between 3 and 20 grains per gallon and dissolved iron is under 5 mg/L. Outside that envelope the resin fouls, and oxidized iron fouls it regardless. That is the line between adding iron duty to a softener you are buying anyway and needing a dedicated filter in front of it. Manganese matters here too, since it behaves similarly and is often present with iron.
The oxidizing filters, and what each needs
A dedicated iron filter works by oxidizing dissolved iron into particles and then trapping them in a media bed that backwashes itself. Air injection draws in a pocket of air with no chemicals to buy. Other beds use a catalytic or manganese-bearing medium, some of which need periodic regeneration with a chemical. Each has a pH range it works within and a maximum iron loading, which is why the test result and not the price should shorten your list.
Why the standards are aesthetic, and why that is not the point
Penn State Extension explains that iron and manganese carry secondary standards set on aesthetic grounds, with recommended maximums of 0.3 mg/L for iron and 0.05 mg/L for manganese. Aesthetic does not mean harmless to your house: iron stains fixtures and laundry, feeds bacterial slimes in the plumbing, and destroys softener resin. Our best iron filter for well water guide covers how the oxidation methods compare in service.
Questions people ask about iron filter for well water
How do I tell what kind of iron I have?
Fill a clear glass. Water that is clear at first and turns orange as it stands carries dissolved iron, while water that is orange straight from the tap carries oxidized particles.
Can my softener handle the iron?
Only within limits: pH above 6.7, hardness between 3 and 20 grains per gallon and dissolved iron under 5 mg/L. Oxidized iron fouls resin whatever the numbers say.
What levels of iron and manganese are recommended?
Secondary standards set on aesthetic grounds give recommended maximums of 0.3 mg/L for iron and 0.05 mg/L for manganese in drinking water.
Does an iron filter go before or after the softener?
Before. Its purpose is to keep iron away from the resin, so it belongs upstream of the softener in the treatment train.