A brass faucet with orange spots is easy to blame on iron in the water, and sometimes iron is the cause. But brass also tarnishes, and cleaners and water minerals leave their own marks. In St. Louis homes, the faucet is a good place to start because you can look at it closely, test simply, and clean it without calling anyone.
What the spots might be
Iron deposits from water are usually orange-brown to rusty red. They tend to appear where water flows or sits: around the spout opening, under the aerator, or in a ring at the base. They may feel slightly gritty when you rub them.
Brass tarnish looks different. It is a surface film that dulls the finish and can darken it or make it look streaky, sometimes brownish or greenish. Some brass also changes color where zinc has leached out of the alloy, leaving a pinkish or reddish surface. Tarnish usually spreads across the whole fixture rather than appearing in isolated spots.
Hard water mineral crust is white or chalky, not orange, so it is usually easy to separate from iron.
Check the pattern first
- Spots only on the hot side point toward the water heater or the hot line, since heater tanks can add rust particles.
- Spots on both hot and cold sides, especially near the aerator, point more toward the water supply.
- Spots only on the top of the faucet, away from water flow, often point to cleaning residue or finish wear.
- Spots that come back within days after careful cleaning suggest a continuing source in the water.
Run a simple water check
Fill a clear glass from the cold tap and let it sit. If orange particles settle to the bottom or the water has a faint rusty tint, iron is a likely part of the story. Repeat with a glass from the hot tap and compare the two. A home test kit can give you a rough reading, and a certified lab can give a more complete answer. Your water utility may also publish an annual water quality report with iron results for your area, which helps St. Louis homeowners see what the supply usually looks like.
Clean without damaging the finish
Brass and coated finishes can be scratched or stripped by harsh cleaners and abrasive pads. Before you clean the whole fixture, test a small hidden spot, such as the underside of the base. Start with a soft cloth, mild dish soap, and warm water. If the orange mark stays, a mild acidic cleaner may help with iron stains. Leave it on only as long as the label allows, rinse thoroughly, and dry the surface. Never mix cleaners, and keep the room ventilated.
For tarnish, a brass polish made for the finish is safer than household scouring powder, which can cut into the surface. Check whether your faucet has a protective lacquer, since polishing or strong acid can remove it and expose the bare metal.
When to get help
If the spots keep returning after cleaning and your water test shows iron, the source is more likely the water supply or the water heater than the faucet. A plumber can inspect the hot tank and supply lines. A water treatment professional can explain whole-house options, but that decision should follow testing, not a single faucet stain.