If your water leaves rust-colored stains in a sink, tub, or toilet bowl, or if it smells or tastes like metal, iron is a likely suspect. Iron is a naturally occurring mineral that moves into groundwater from rock and soil, and it shows up in some St. Louis wells and in some older pipes. Before you buy a filter or call anyone to service your system, you need to know whether iron is actually present and roughly how much there is. Two routes can answer that question: a quick test you run yourself, and a sample sent to a state-certified lab.
Why a simple test is not the whole answer
Staining, odor, and taste are useful clues, but they do not measure anything. Other things can stain fixtures too, including manganese, copper from plumbing, and tannins from decaying plant matter. Iron can also be present without any obvious sign, especially when it is dissolved and clear when it comes out of the tap and only turns orange after it sits in air. That is why a sample taken at the right time and tested with a proper method matters more than a guess based on color.
Home test kits
Inexpensive home kits come in two common forms. Test strips are dipped in a sample and compared to a color chart. Drop kits use a small amount of reagent added one drop at a time until the water changes color. Both can help you decide whether it is worth paying for a full lab test.
- Strips are fast and easy, but the color matching is rough and results can vary between readings.
- Drop kits take more patience, but they tend to give a more controlled reading.
- Neither type can tell you whether the iron is dissolved, particulate, or bound to bacteria, and neither gives a report you can share with a service provider.
- Check the expiration date on any kit, and store it away from heat and sunlight.
When to send a sample to a lab
A certified lab is the right choice when you want a number you can trust, when you are buying a home, when you are planning a treatment system, or when you have a private well and need a baseline. Many labs in and around St. Louis accept drinking water samples, and most will explain what each test measures if you call before sending the sample.
- Ask the lab to test for total iron and for dissolved iron, since the two results point to different treatment options.
- Ask whether the lab also tests for manganese, because the two often show up together and look similar in stains.
- Confirm the lab is certified for the test you need, and ask how long results usually take.
- Ask for the report to list the detection limit, so you can tell a true zero from a result that was simply too low to measure.
How to collect a clean sample
Sample collection affects the result as much as the test itself. Iron can oxidize and settle in the bottle, so the way you fill it matters.
- Use the bottle the lab provides, and do not rinse it with anything other than tap water unless the lab instructs you to.
- Run the cold tap for a few minutes before filling, but do not run it so long that you draw water from a different part of the system than you intend to test.
- Fill the bottle without splashing, and cap it right away to limit contact with air.
- If you are testing for dissolved iron, the lab may ask you to add a preservative or to filter the sample on site. Follow their directions exactly.
- Write the date, time, and tap location on the label, and send the sample as soon as the lab allows.
Reading the results
A lab report lists what was measured in a standard unit and compares it to the level the lab or a water utility uses as a reference. Iron is generally discussed in terms of staining and taste rather than as a health concern, so the report mainly tells you whether you are likely to see staining, whether a filter or oxidizing treatment is needed, and whether the iron is mostly dissolved or mostly solid. If the report shows a result near the detection limit, a repeat test is worth considering before you spend money on equipment. If it shows manganese along with iron, say so when you talk to anyone who might service your system, because treatment choices can differ.
What to do next
Start with a simple observation of where the staining appears and whether it happens with hot water, cold water, or both. Then run a home test to see whether iron is likely present. If you have a private well, or if the staining is serious, send a certified sample to a lab and keep the report with your home records. Once you know what is in your water, you can compare options with clear questions in hand, rather than relying on a guess about what the stains mean.