If orange water comes out only when you open the hot tap, that pattern is a useful clue. Iron in groundwater or city supply usually shows up on both the hot and cold sides. When the color appears only on the hot side, the water heater, the hot pipes, or something that changed inside the tank becomes a more likely cause. This guide walks through a simple way to sort it out in a St. Louis home before you decide what to do next.
Start With a Side-by-Side Check
Pick one sink or tub and run the cold tap alone until the water runs steady, then fill a clear glass. Do the same with the hot tap. Hold both glasses against a white sheet of paper in good light so you can compare the color. Then repeat the check at a second fixture, such as a kitchen faucet or a laundry sink.
- Orange in both hot and cold at every fixture: the problem is probably in the supply or in a treatment system that serves the whole house.
- Orange only on the hot side: focus on the water heater and the hot line.
- Clear cold water, orange hot water at one fixture only: check that fixture and its own hot supply line first.
Check the Water Heater
A water heater holds a large volume of water at a higher temperature than your cold lines, so it can collect sediment and show corrosion more readily. Before you touch anything, turn off the power or gas to the heater as its manual directs, and let the water cool. Then open the drain valve near the bottom of the tank and run a small amount into a clear bucket. Look for flakes, grit, or a steady orange tint.
Heavy flakes or grit suggest sediment or internal corrosion, which is a separate problem with its own cleanup steps. If the water is only faintly orange and the tank is otherwise quiet, the heater may not be the main source, and the hot line deserves a closer look.
Many tanks also have a sacrificial anode rod, a metal rod that corrodes so the tank itself does not have to. If that rod is heavily worn, the tank may be corroding from the inside. Checking it usually requires removing the rod, so this is a job for a licensed plumber unless you have done it before and know the process.
Look at the Hot Water Line
Hot water pipes can corrode from the inside, especially in older homes. Some St. Louis houses still have steel or galvanized piping in parts of the plumbing, and those materials can shed rust over time. The pattern of the color can help you tell the difference.
- If the water is strongest in the first draw after the hot tap has sat unused for a long stretch and then steadily clears, the pipe itself may be shedding rust in stagnant sections.
- If the water stays orange at the same steady level no matter how long you run it, the source is more likely the water entering the heater or a treatment unit ahead of it.
Look for other clues as well. Rusty staining on the outside of the heater connections, a dripping valve, or rust on nearby fittings can point to a leak or corrosion at the point of connection. Those signs call for a plumber, not a home fix.
Check for Treatment Equipment
If you have a water softener, an iron filter, or another treatment unit, look at how it is set up. A filter that is backwashing or a softener that needs servicing can change how iron appears at the taps. Water that passes through a treatment unit can also look different on the hot side if the heater sits after the unit. Read the equipment's manual or ask the person who services it how the water flows through the system.
Simple Tests Versus a Lab
A home test kit can show you whether iron is present and roughly how strong the color is, which is enough to decide whether the problem is worth pursuing. It cannot tell you the exact amount of iron, and it cannot confirm the cause on its own. If the orange color is strong, if it appears at both hot and cold taps, or if you are planning to install treatment equipment, a certified laboratory test gives you the detail you need. Your water provider can also tell you what they report for your area, which is useful context but does not replace testing at your own tap.
What to Do Next
- Compare hot and cold at two or more fixtures and note which side shows the color.
- If only the hot side is orange, drain a sample from the water heater and check for flakes or grit.
- Look at the hot line and the heater connections for leaks, drips, or outside rust.
- Check any treatment equipment for backwash cycles, service dates, or error lights.
- If the problem persists or involves a heater with heavy sediment, call a licensed plumber to inspect the tank and anode rod.
Keep notes on the date, the fixture, and the color you saw each time. Those notes make it easier for a plumber or testing lab to narrow down the cause quickly.