Orange or brown stains on a sink, inside a toilet bowl or on white laundry look like rust, so most homeowners assume their pipes are corroding. Sometimes that is right. Dissolved iron is a different problem. It is already in the water when it reaches your house, it is invisible when the water is first drawn, and it turns orange-brown once it meets air. Before you ask anyone to size or sell equipment, confirm which problem you have.

Run a sit test on a clear glass

Fill a clear glass or jar from the cold tap at the kitchen sink, set it on the counter, and look at it after about ten minutes. Rust from pipe scale usually shows up as grit or flakes that are already in the glass when you pour, and they settle to the bottom. Dissolved iron often looks clear when poured, then develops a faint yellow or orange tint, sometimes with a film on the surface, as it oxidizes. A color that appears while the water sits, rather than particles you can see at once, points toward iron. Repeat the test at a hot tap and compare. If the hot and cold samples behave differently, note that, because it tells you something about where the problem starts.

Check where the stains show up

Iron stains tend to appear where water sits and then dries: the waterline inside the toilet bowl, the rim of a basin after a dripping tap, the edges of a tub, and the base of a faucet. Pipe rust tends to show as specks you can wipe off or as debris caught in an aerator screen. Staining that returns soon after a thorough cleaning, and that shows up on cold-water fixtures, fits dissolved iron better than a one-time flake problem.

Look at the toilet tank as well. A reddish-brown slimy film inside the tank, sometimes with a sour smell, can come from iron bacteria, which feed on iron. That film is a sign to ask the tester about iron and bacteria directly, not a reason to start treating the house on your own.

Laundry is useful evidence too. Iron leaves rust-colored marks on white fabric that ordinary detergent does not lift, and the marks can appear even when the water looked clear in the glass.

Separate iron from the look-alikes

Hardness leaves white scale and spots, not orange staining. Manganese tends to leave black or dark brown marks, and it often shows up in the same water as iron, so it can be easy to misread a stain color. If the marks are dark brown or black, ask the lab to report manganese separately instead of assuming iron explains the whole picture.

If your neighbors on the same street report the same stains, the cause may be in the public supply rather than your plumbing. In that case, the water utility is the first place to ask what it has measured in your area.

What to ask for on the water test

  • Iron, reported as total iron and as dissolved (ferrous) iron, in milligrams per liter.
  • Manganese, reported on its own line.
  • pH and hardness, since both affect how iron behaves and which equipment is suitable.
  • Where the sample was drawn, and whether it was taken before any filter or softener. A sample taken after treatment says nothing about the source.
  • Whether the tap had been running or had been sitting unused. Standing water can change iron readings, so the lab should say which case the number reflects.

What a proposal has to match

Once you have the numbers, ask each provider how its proposal is based on your report. Ask whether the equipment is rated for dissolved iron at the level you measured, and whether it can also handle the other minerals in the sample. Ask how the system removes or oxidizes iron, how often it needs cleaning or a media change, and what happens to the backwash water. A provider that quotes equipment without asking for the report, or that only offers a general description of iron treatment, has not yet matched the equipment to your water.

Keep the test report with your other paperwork. You will need it to compare proposals and to check whether a system is doing the job it was sold for. For how this site judges claims about testing and equipment, see the Review Methodology and Editorial Criteria.