Brown, yellow, or orange water usually means iron, rust, or sediment, but the color alone does not tell you where it started. It can come in from the street supply, be stirred up in the service line between the meter and your house, or be generated inside your own water heater. Each source has a different fix, so the first job is to sort the problem by where you see it.
Start with the pattern at each tap
Go to the kitchen sink and run the cold tap, then the hot tap, then a tap in another room. Write down what you see at each one. Discoloration at both hot and cold taps throughout the house points to the supply or the service line. Discoloration only at the hot tap points to the water heater, where sediment and rust collect in the tank and the anode rod can shed debris. Discoloration at a single fixture points to that fixture, its aerator screen, or one branch of pipe.
Check whether it clears and whether it comes back
Run the cold tap for several minutes until the water runs clear. Then let the house sit for several hours or overnight and run it again. If the color returns and then clears after a few minutes of running, that is typical of sediment or rust that was disturbed in the pipes. If the water stays clear, the cause was probably a short disturbance. If it stays discolored no matter how long you run it, the source is steady and needs testing before you choose any equipment.
Also note the timing. Discoloration that appears only on the first hot draw after the house has been quiet points to the heater. Discoloration that appears when someone runs a washing machine or a dishwasher points to the supply or the service line.
Look for a utility event nearby
Ask your water provider whether they have worked on nearby mains, flushed hydrants, or had a break in your area around the time the color started. Ask whether neighbors on your street have reported the same thing, and whether they will test the water at your meter. Get the answers in writing, along with the date and time the provider lists for any work, so you can match it against when you first noticed the color.
Read the stains, not just the water
Rust-colored stains on white sinks, toilet bowls, and laundry suggest iron or manganese in the supply. Blue-green stains on copper fixtures can point to water that is corrosive to pipes. Black specks that show up at the aerator or in the first draw from the hot tap are often debris from the heater, or from a pipe scale that was loosened. Compare what you see with the tap pattern above before you assume the cause.
What to ask before you buy treatment
Do not buy a filter until you know what is in the water. Ask the provider or a testing lab whether the results show iron, manganese, or sediment, and at what levels. Ask whether the test covers the water at your meter or only at the treatment plant. Compare the report to the published results your provider makes available, and use the county overview on St. Charles Water Ratings to see how local supplies are described. A sediment filter, an iron filter, or simply a heater flush each fit a different cause, so the right answer depends on the test rather than the color.
For the heater, ask a licensed plumber whether the tank should be drained and flushed, whether the anode rod needs inspection, and whether the heater itself is near the end of its service life. Ask for the findings in writing.
When to stop using the water and call
If the discoloration comes with a strong odor, a sudden drop in pressure, or cloudy water that does not clear, call your water provider now and ask whether you should use bottled water until the issue is resolved. If anyone in the house drinks the water or uses it to mix infant formula, do not wait for a schedule. Call the provider and ask about safety before the next use.