Orange or rust-colored stains under a kitchen sink are one of the most common things St. Louis homeowners notice and then wonder about. Iron in water is one possible cause, but it is not the only one. A slow leak from a supply line or the drain can leave the same color behind. Before you buy a test kit or call someone out, look at the pattern, the water, and the pipes.
Start with the shape and location of the stain
Stains from iron in water tend to appear where water sits, dries, and returns again and again. Stains from a leak tend to start at one spot and spread outward. Check the following:
- A stain that forms a ring or a thin film on the cabinet floor, sink bowl, or drain area after running the tap points toward your water supply.
- A stain that grows wider over time, feels damp, or gives off a musty smell points toward moisture from a drip.
- A stain on the back wall of the cabinet, near the shutoff valves or the flexible supply lines, points toward a connection that is weeping water.
Check for a leak first
A small leak can corrode metal fittings and carry rust particles into the wood or particleboard below. That is why a leak often looks like iron. To rule it out, follow these steps:
- Dry the cabinet floor completely with a towel.
- Place a dry paper towel or a strip of cloth under each supply line, the shutoff valves, and the drain trap.
- Run the faucet for a minute, then turn it off and leave the cabinet alone.
- Check the paper and the cabinet floor again later in the day, and again the next morning.
If the paper is wet or the wood is soft, tighten the connection gently by hand first. Do not force a fitting, because that can crack it. If the problem continues, a plumber can replace the part.
Look at the rest of the house
Iron in the water usually shows up in more than one fixture. If you also see orange marks in the bathtub, the toilet bowl, the laundry, or on white fixtures in general, the water supply is the more likely source. A leak will usually stay in one area, while water chemistry tends to leave marks in several places.
Keep in mind that iron is a naturally occurring mineral found in groundwater. Its presence in water is a question of what is in the supply, not a sign of anything wrong with your home or your household.
Test the water yourself
Home test kits for iron are sold at many hardware and home supply stores in the St. Louis area. Read the directions carefully and follow them exactly, since small mistakes can give misleading results. Test cold water from the kitchen tap after the water has run briefly, and test hot water separately, because a water heater or hot water line can contribute its own rust.
If you want a more detailed answer, a certified water testing lab can measure iron and other items in a sample you collect and send in. Ask the lab what it tests for and how to collect the sample.
Many homes in the St. Louis area receive water from a municipal supply. The provider publishes an annual water quality report, and it is a useful place to see which items have been measured in the water that leaves the treatment plant. That report does not show what happens inside your own pipes, so a stain in your kitchen may still come from your plumbing. If your home uses a private well, testing is your responsibility, and it is worth doing on a regular schedule.
Clean the stain safely
Stain removal is only a temporary fix if the source is still active. Once you have a plan for the source, you can clean the area. Use a cleaner made for rust or hard water on hard surfaces, and test it on a hidden spot first. Avoid mixing cleaners, especially bleach with other products. Rinse and dry the area thoroughly. If wood or particleboard has swelled or softened, remove and replace the damaged section, because stains will keep returning from the material itself.
When to get help
- Call a plumber if you find a wet connection, a worn supply line, or a drain that drips.
- Use a certified lab if you want a clear answer about the water itself, especially if the stain appears in more than one fixture.
- Contact a water treatment professional only after you have test results, so you know what the water actually contains.
Start with the simple checks. Most orange stains under a St. Louis kitchen sink become clear once you separate a leak from the water supply.