Iron
Orange-brown staining, metallic taste, and the reason your laundry looks rusty.
- Safe range
- 0 – 0.3 mg/L
- Ideal range
- 0 – 0.1 mg/L
- Measured in
- mg/L
What it is
Iron dissolves into groundwater from surrounding rock, and can also come from corroding steel or cast-iron pipework. Dissolved iron is clear when drawn and turns orange-brown as it oxidises in air, which is why a glass can look fine at the tap and stain the sink an hour later.
Why it matters
Iron is an aesthetic parameter rather than a health one at the levels found in water; it is a dietary mineral, and the amount in water is small next to food. What it costs you is staining on fixtures and laundry, a metallic taste, and the iron bacteria that sometimes accompany it and produce a distinctive slimy build-up.
How to measure it
Strips give a workable answer, and a glass of water left to stand tells you which kind of iron you have, which is what decides the treatment.
Test strips
- How trustworthy
- Ballpark
- Cost
- Low cost
- Effort
- Under a minute, wherever you drew the sample
A plastic strip with reagent pads on it. Dip it, hold it level, and match each pad against the chart on the bottle at the time the label tells you to. Most strips read several parameters at once.
Iron strips read a wide range and are honest about whether iron is behind your staining.
Where to find it: Pool shops, hardware stores, supermarkets and online, sold both per parameter and as multi-packs. Buy strips made for your kind of water: pool strips and drinking water strips read very different scales for the same chemistry.
What you can see, taste and feel
- How trustworthy
- Ballpark
- Cost
- Free
- Effort
- None
Not a measurement, and it belongs here anyway: it is free, it is continuous, and it is what tells most people to test at all. Treat it as the prompt for a number, never as the number.
Fill a clear glass and leave it. Water that is clear when drawn and turns orange-brown over the next hour carries DISSOLVED iron; water that is rusty the moment it arrives carries particles that have already oxidised. A slimy reddish film in the cistern is iron bacteria, which is a third problem with a third answer.
Where to find it: A clean, clear glass and a sheet of white paper.
Certified laboratory, mail-in kit
- How trustworthy
- Reference grade
- Cost
- Most expensive
- Effort
- Careful sampling, then days or weeks of waiting
You are posted bottles and instructions, you fill them exactly as told, and you post them back. Weeks later a report arrives with figures nobody has to interpret by eye. This is what a result you intend to act on should be built from.
Puts a number on it and separates iron from manganese, which stains black rather than orange and is treated similarly but not identically.
Where to find it: State-certified drinking water laboratories; your state's certification officer keeps the list, and many public health departments will point you at one.
Your utility's annual water quality report
- How trustworthy
- Reference grade
- Cost
- Free
- Effort
- A few minutes of reading
Every community water system in the US has to publish one each year, free, listing what it found and what the limits are. It is real laboratory data about the water leaving the plant and travelling the mains. What it cannot describe is your own plumbing.
Published by most systems as a secondary standard. If your supply reads low and your sink does not, the iron is coming from your own pipework.
Where to find it: Your water bill, your supplier's website, or the EPA's index of reports. It is also called a Consumer Confidence Report or CCR.
Taking the sample
For several of these the sample is where the error is, and no instrument recovers from a bad one.
- • Sample from a tap ahead of any treatment, then take a second sample after it, so the pair says what the unit is removing.
- • If the staining started recently in an older house, take one from an outside tap as well. Corroding pipework produces iron the supply never sent you.
If it is too low
Low iron. Nothing to act on.
- • No action needed.
If it is too high
Orange-brown staining on sinks, baths and laundry, metallic taste, and occasionally a slimy residue where iron bacteria are present.
- • Oxidising filters or greensand filtration handle dissolved iron.
- • A softener removes moderate iron as a side effect of removing hardness.
- • If the staining started recently in an older property, suspect corroding pipework rather than the source water.
Common questions
Is iron in drinking water harmful?
Not at the levels found in water supplies. Iron is regulated as a secondary contaminant in the US, an aesthetic standard covering taste, colour and staining rather than a health-based limit.
Why is my water clear at the tap but turns orange later?
Because the iron is dissolved when it arrives and oxidises on contact with air. Clear water that browns on standing is the classic signature of dissolved iron, as opposed to rust particles, which are visible immediately.
WiseWaterGauge helps you record and understand your own readings. It is not a substitute for a certified laboratory test, and nothing here is medical or regulatory advice. If a health parameter is out of range, confirm it with an accredited lab and speak to your water provider.