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Iron, Sulfur & Filters

What a softener cannot fix, and what handles each problem.

How do you remove 3 ppm of iron from well water at pH 7?

3 ppm iron at pH 7
oxidising iron filter
at pH 7 the iron is already oxidised — a softener will not hold it, whatever the concentration says
3 ppm iron at pH 73 ppmIron0.3 ppmEPA threshold
Treatmentgreensand or catalytic media oxidises the iron, then traps the particlesoxidising iron filter
Typical installed cost$1,200–2,500
Iron form at this pHcloudy straight from the tapferric (oxidised)
IronEPA secondary standard is 0.3 ppm3ppm
EPA threshold0.3ppm
Load added to a softenerabout 4 gpg of hardness capacity per 1 ppm of iron12gpg equivalent

Notes

  • pH decides the method, and almost nobody measures it. Below pH 7 iron is dissolved — the water looks clear at the tap and stains minutes later. At pH 7 it is already oxidised, so it arrives as particles and the water is cloudy from the moment it leaves the tap. This single number is why advice online contradicts itself: everyone is right for their own pH.
  • A softener is the wrong tool here. 3 ppm would normally be inside a softener's range, but at pH 7 the iron has already turned to particles, and particles foul the resin bed instead of binding to it. The softener stops softening and the water stays stained — the most common expensive mistake in well water treatment.
  • Treat iron before the softener, never after. Whatever the method, iron removal goes first in the line. A softener downstream of clean water lasts; a softener taking raw iron is a filter that was not designed to be one.
  • Get a real lab test, not a strip. You need iron, pH, manganese, hardness and — if there is a smell — hydrogen sulphide. Manganese behaves like iron but stains black instead of orange, and it needs a higher pH to oxidise. A test strip gives you one of those five numbers, badly.
  • Iron bacteria are a different problem with the same symptom. If there is orange slime in the toilet cistern rather than a stain, no filter will fix it — that needs shock chlorination of the well itself first.

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Iron removal

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