Rusty hot water is not only unpleasant to see, it can smell bad, taste bad and stain clothing instead of cleaning it. In rare circumstances, it can even signal dangerous contamination in your water supply. If the problem really is rust, it is merely an inconvenience. If you think your water may actually be contaminated, however, get it professionally tested as soon as possible.

Built-up Sediment

One of the most common causes of rusty hot water is built-up sediment in the hot water heater. Small traces of rust and dirt from the water supply can accumulate as water is pumped through the hot water heater. This water settles on the bottom of the heater tank. When the tank is suddenly turned on, it stirs up the water and sends a burst of brownish sediment down through the water line, making the hot water come out of the tap brown at first.

Compromised Water Tank

A water tank is normally shielded by a glass jacket, which stops the water from coming into contact with the outer wall of the tank. If this jacket starts to feel, the hot water can leak through and contact the metal wall. This will slowly rust out the tank, turning the hot water brown and eventually causing the tank to leak.

Compromised Piping

A couple things can happen to the piping to turn the hot water brown. The simplest problem is that you are simply using old piping. Certain iron pipes can start to rust as they age, and the hot water can cause the rust to break loose, turning the water brown. A more serious problem is contamination. If your pipes are not properly sealed, dirt can slowly leak into them from outside. This dirt may look rusty, but is actually contamination from the soil around the pipe.

Iron Bacteria

Most water naturally contains a small amount of dissolved iron. Iron bacteria are small organisms which turn this dissolved iron into iron oxide, also known as rust. They often thrive in wells, and can also breed in a hot water heater. These bacteria will make your pipes rust more quickly and make your water taste bad and discolor clothes.

Prevention/Solution

First, start with the water heater. Drain the water out of it to flush the system and see if the problem goes away. If that doesn't work, look at the heater. Is it particularly old? Does it look rusted or in need of repair? Next, check out your piping. Replace black iron pipes, pipes with rusty joints or old, leaky plumbing. If neither of these methods works and you leave near a well, you may have to use shock chlorine treatment to get rid of iron bacteria. Follow the link below for more information.