Why is my hot water rusty?

By Dana Whitlock. Updated October 2026. Repair or replace?

Rust-colored water from the hot side only is a warning about the heater. Every glass-lined steel tank relies on a sacrificial anode rod that corrodes so the tank does not. When the rod is used up, the steel starts to rust from the inside. Rheem lists brown or reddish water as a sign of corrosion or a deteriorating anode. With luck, you have caught it early enough for a new rod to buy time.

Likely causes

A spent anode rod Pro job

The rod dissolves slowly over years. Once it is mostly gone, the tank loses its protection. A plumber can pull it and judge how much remains. That is a job for a pro, since it takes a large socket, tank draining, and sometimes cutting room overhead.

Corrosion inside the tank Pro job

If the rod failed long ago, the tank lining may already be rusting. Rheem says persistent discoloration suggests the unit is nearing the end of its life. A rusting tank eventually leaks.

Galvanized or old iron pipes Safe to check

In older homes, steel supply pipes can rust inside and color both hot and cold water. Run the cold side to tell whether the pipes or the heater are to blame.

Utility main work Safe to check

Main breaks or hydrant flushing can stir up sediment and briefly discolor all water in the house. It usually clears after the cold taps run for a while.

Safe things to check first

• Run a cold tap for a minute. Rusty cold water points to the pipes or the utility.
• Run a hot tap. Rust that appears only on the hot side points to the heater.
• Look at the base of the tank and the fittings on top for rust streaks or seepage.
• Check for a crusty white or rust-colored stain under the drain valve.
• Note how long the heater has been in place, or find the install date on its label.

When to stop and call

Book a licensed plumber to inspect the anode and the tank if discolored water comes only from the hot side. Call the same day if you also see water at the base, since a rusting tank can split. If the relief valve has started dripping or you smell burning near an electric unit, switch off its breaker and call. Smell gas? Leave the house first, then call the gas utility from outside.

Repair or replace?

Start with its age. Type the serial from the label:

Rusty hot water on a heater past its expected life is a strong replace signal. DOE's analysis gives about 14.5 years for an average gas tank and 15.1 for electric, and inspector charts list as little as 6 to 12 years for conventional heaters. Date yours with the age decoder above. Under eight years with a dry tank, a new anode is reasonable. Older than that, or with rust showing on the outside, compare the replacement range above against the cost of an anode and a near-term leak.