Rust-colored water from a tap is one of the most common things homeowners in St. Louis notice, and it is easy to misread. The color can come from the water entering the house, from the pipes or water heater inside the house, or from sediment stirred up in the line. Which taps show the problem, and whether it appears on hot, cold, or both, is the first clue.
What the color usually means
Iron is a naturally occurring mineral in many groundwater and some surface sources. When dissolved iron meets air, it oxidizes and turns reddish or brown. That can appear as a tint in a glass, orange or brown staining in sinks and tubs, or fine particles in the water. Rust from older iron pipe or a corroded water heater can produce a similar look. With iron, the main concerns are usually staining and taste, but the source still matters because it determines the fix.
Start with the pattern
Before you test anything, note which taps show the problem and when.
- Cold only, at every tap: points toward the water entering the house or a supply line near the meter.
- Hot only: points toward the water heater, its dip tube, or the hot water piping.
- Both, but worse on hot: often the water heater or a shared supply issue.
- Only after the house sat empty or the water sat overnight: can be stagnant water or rust that built up in idle lines.
- Only after work on the street or a nearby main: sediment that was stirred up, usually clearing with regular use.
Check the cold line first
- Fill a clear glass from the cold kitchen tap and hold it against a white background.
- Run the cold tap until the water looks clear, then fill a second glass and compare.
- Check whether the color returns after the water has sat for a while. Water that clears and stays clear points away from the street supply.
- Unscrew the aerator on the faucet and look inside. Loose particles caught there often mean sediment came through the line.
Check the water heater
If hot water is the problem, the water heater is the usual suspect. Shut off the power or fuel to the heater before working on it, and follow the manufacturer's instructions for the drain valve. Drain a small amount of water into a clear container. Rusty or dark sediment in the sample suggests the tank has built up deposits or that the anode rod is corroding. A tank that has not been flushed in a long time may also need service. A licensed plumber can inspect the anode rod and the dip tube, and can tell you whether flushing will help.
Look at the house plumbing
Older homes in St. Louis may still have galvanized steel piping in parts of the house. Galvanized pipe corrodes from the inside, and rust can flake off over time. If the color shows up at several fixtures and the house has older pipe, a plumber can look at the pipe material and its condition. Do not assume the whole system needs replacing based on color alone.
Test the water
A home test kit for iron can give you a rough reading, and many certified labs test for iron, manganese, and other minerals. Ask the lab to explain the result in plain terms, then compare it with the guidance from your water provider. Your provider publishes an annual water quality report, which is worth reading for what it says about the supply. If the report lists iron or manganese, that is a useful starting point, but it describes the supply in general. A test at your own tap shows what reaches your fixtures. Also check what any treatment equipment you own is rated to handle before assuming it will address iron.
When to call for help
- Color that persists at every tap after you have run the lines.
- Heavy sediment from the water heater drain.
- Staining that keeps coming back after cleaning.
- Any work on the supply line or the meter, which should be handled by a licensed professional.
If the color appears suddenly and across the whole house, contact your water provider and ask what they recommend before you continue using the water as usual. Keep a simple record of what you saw. Write down the date, which taps were affected, whether the color cleared, and how long it took. That record helps whoever looks at the problem next, whether that is the provider, a plumber, or a testing lab.