Orange or rust-colored stains in your toilet bowl and sinks usually come from one of two places: iron in the water supply, or iron bleeding out of corroding pipes inside your home. Figuring out which one is the starting point for fixing it.
The Two Main Sources
Iron in the water supply. This is the most common cause, especially in homes on well water. Even a small concentration of dissolved iron, as little as 0.3 mg/L (the EPA’s secondary standard), can leave reddish-brown rings in toilet bowls and sink basins. The iron oxidizes when it hits air or chlorine and drops out of suspension as rust-colored particles. If you’re on municipal water, the supply itself is usually low in iron, but aging distribution mains can contribute, particularly after nearby construction or a main break.
Corroding galvanized steel pipes. Homes built before the 1970s often have galvanized supply lines. Over decades, the zinc coating wears away and the steel underneath rusts from the inside out. The rust flakes and dissolves into the water and ends up deposited on your porcelain. If your stains got noticeably worse in the last year or two, or if you’re also seeing discolored water when you first open a faucet in the morning, galvanized pipe corrosion is a strong candidate.
Water heater tank. A failing anode rod or a tank that’s past its service life can also contribute rust-colored water, but only to your hot-water fixtures. If you notice the staining is worse at the hot-water side of your sink (or in the shower) and minimal in the cold-only toilet tank, put the water heater at the top of your list.
How a Plumber Diagnoses It
A licensed plumber will typically run a simple iron water test first. There are also field test kits that can distinguish between ferrous iron (dissolved, keeps water clear), ferric iron (already oxidized, turns water cloudy or orange), and iron bacteria (which form a slimy reddish biofilm in the toilet tank rather than hard staining).
They’ll also check pipe material. Dull gray threaded pipe at an access panel is galvanized steel; copper or PEX means a previous upgrade already happened. A plumber can also measure water pressure across the house, because heavily corroded galvanized pipes narrow over time and reduce flow noticeably.
If the source is the water heater, they’ll check the anode rod condition and the tank’s age. Most tank water heaters are rated for 8 to 12 years. A corroded anode rod can often be replaced without replacing the whole unit, but a tank that’s already rusting through needs to come out.
What You Can Check Yourself
You can do a few things without calling anyone yet.
Lift the lid off your toilet tank (not the bowl, the tank behind the seat). If you see reddish-brown slime or a rusty film on the sides of the tank, that’s often iron bacteria, not just mineral deposits. Iron bacteria aren’t a health hazard but they are stubborn.
Fill a clean glass from your cold tap and hold it up to light. If the water runs clear and only stains the fixture over time, you’re dealing with dissolved ferrous iron. If the water is visibly orange or has visible particles, the problem is more acute.
Check whether the staining is consistent across the whole house or worse at specific fixtures. A single corroded supply stub-out can affect one sink without affecting the others.
Run the cold water in a tub for a minute or two after it’s been sitting. If the water clears up after running, the rust is sitting in the pipes themselves, not coming in from the street.
What Needs a Licensed Plumber
Replacing galvanized supply lines is not a DIY job. The fittings are threaded, often corroded, and prone to cracking under torque if you don’t know the condition of the downstream pipe. One cracked fitting inside a wall is a much worse problem than the staining you started with.
Water softeners and whole-house iron filters can address iron in the supply, but sizing them correctly requires knowing your actual iron concentration, water hardness, and flow rate. An improperly sized system either won’t solve the problem or will introduce new maintenance issues. A water treatment specialist or licensed plumber can pull a water sample and spec the right unit.
If your water heater is more than 10 years old and contributing rust, replacement is usually the better call compared to trying to extend its life with an anode rod swap. That’s a job for a licensed plumber.
When to Call a Pro
Call a licensed plumber if:
- Your staining is getting worse over months, not better
- You see visible rust particles in the water, not just staining
- Water pressure across your home has dropped noticeably
- Your water heater is older than 10 years and producing discolored hot water
- You have galvanized supply pipes and haven’t had them inspected
In California, plumbing work on supply lines and water heaters requires a licensed contractor. You can verify a plumber’s license at cslb.ca.gov before any work starts. It takes about 30 seconds and protects you if something goes wrong.
Iron staining doesn’t go away on its own. Once you’ve narrowed down the source using the checks above, a licensed plumber can give you a proper diagnosis and lay out your options, so you’re not guessing at a fix or buying equipment that doesn’t match your water chemistry.