Water Heater Corrosion, Rust and Brown Water in Plumbing

Is your water heater leaking due to corrosion? Is there a leak from the rusty plumbing? Find out what is corrosion, rust, corrosive water, and how it can affect your household. Check out what is that brown water coming out of the fixture, why it's happening, and how to prevent it.

Corrosion in water heaters and plumbing is not good. This is not only an aesthetic concern or small issue that causes a low water flow, brown water, and high-energy bills but also a safety problem, as the corroded and damaged elements can cause structural damage and health-related complications.

What is corrosion?

Corrosion is a process where the metal changes its structure – deteriorates due to a chemical reaction with the surrounding environment. It can also occur to nonmetals. Read more in this wiki article.

What is rust?

Rust occurs when metal that contains iron forms iron oxide (due to corrosion) in the presence of oxygen and moisture and is recognized as the reddish-brown crust.

Types of corrosion

There are different types of corrosion, and the following two are the most common in plumbing and water heating systems. Most of the time, corrosion occurs to an older water heater and piping, but it can be seen in new installations as well.

Galvanic or electrolytic corrosion

Galvanic or electrolytic corrosion occurs when two different materials are in contact via an electrolyte. A typical example is the water heater, where the anode rod is made of magnesium, a water tank is made of steel, while the electrolyte is water. In this case, the deterioration occurs as the molecules of one material are drawn toward the molecules of the other material, resulting in a chemical reaction - corrosion.

This is why an anode rod is called a sacrificial rod, and its rate of corrosion is increased as the water becomes hotter or acidic. As the water tank is made of steel and acts as the cathode, the anode rod had to be made of the material which can be attacked first protecting the metal tank - so zinc, aluminum, and magnesium are found to be the best options for the anodes.

Atmospheric corrosion

Atmospheric corrosion, also known as oxidation, is caused by the moisture and gases found in the air. For example, ferrous metals, such as iron, when exposed to the air, form iron oxide or, as we know it - rust. Every molecule is affected by this reaction until the metal rusts away completely. Non-ferrous materials are not affected by corrosion in this case.

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Problems caused by corrosion

Water that is in contact with the rust is not safe to drink, wash, and any other use. 

Rusty or corrosive water may look and taste unpleasant (bitter) and can also stain your clothes.

Due to the presence of toxic material, it can lead to health problems. If you have a safety concern, the best will be to talk to the utility company.

Contact a licensed plumber if the repair is needed, or you are required to treat the water and make it non-corrosive.

Deteriorated pipes with the rust that flakes off can clog the plumbing or cover the water heater elements, creating low water flow, low performance, and the environment for bacteria growth.

Another big problem is when the water heater is leaking due to tank corrosion. The only solution for this issue is to replace the unit. 

If it is only a corroded pipe that is leaking, a solution is to replace the damaged section.

How to recognize corrosion

Rusty waterImage source: Pixabay

Almost every water heater and plumbing system during its lifetime corrode, more or less. 

The visible signs are rust, brown water coming out from the home faucets, and a puddle of water, usually under the crack.

Rust is easy to recognize. It usually has a brownish color, and it flakes off the metal surface.

If the water heater tank is leaking due to inside corrosion, there is usually an orange/brownish streak on the outside surface of the tank or a puddle of reddish-brown water at the bottom of the unit. 

Besides, if the water comes from the wells, it can contain a small amount of dissolved iron. Small iron bacteria use this iron, which turns into iron oxide or rust, making your hot water brown at the tap.

Water heater corrosion

As the water heaters are mainly designed with the metal tanks, they are also affected by the aggressive water action, while those with the plastic tanks, such as Rheem-Marathon, are not.

To protect against corrosion, the manufacturer covers the metal tanks with the glass lining and installing the anode rods. The glass enamel, which protects the water heater tank from the aggressive water action, can be broken, exposing the metal surface to rust, while the anode rod can be consumed and inactive.

If the manufacturer provides a longer warranty on its water heaters, such models have better corrosion protection, including two or more anode rods, commercial-grade type, or powered anodes.

There are also gas and oil-powered boilers - used for water heating but do not have glass liners or the anode rod. The great advantage of such boilers is the water storage tank, built from the quality materials such as stainless steel. 

Rust on the metal parts first shows up as a red/brown (blue/green) flaking, and if not serviced correctly and on time, it can turn into series damage.

The problem with the anode rod is when corroded away, so the rust particles drop onto the bottom of the tank, where it mixes up with water, increasing the risk of being used by the user.

Note: Many experts would recommend draining and flushing a water heater, but if the tank-type unit is over 20 years old, you can expect some severe leaking as time passes by. Consider buying a new one, especially energy-efficient.

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Tankless and corrosion

In a case of the tankless water heaters, corrosion can also occur, but rarely, because water gets in contact with the heater's components only in a short period, plus the heat exchangers are made of copper and stainless steel. Since the heat exchanger stores only a small amount of water, this is where the corrosion might happen. The advantage of the tankless models is that their parts can be easily replaced if corroded.

Plumbing corrosion

All the metal pipes that are used in plumbing can corrode at a certain point. Even stainless steel and copper piping can corrode.

Rusting is an indication that the piping system and other elements deteriorate over time with the potential for failure and leaking. Galvanized pipes, for example, first corrode at the threads while copper pipes rust at the connection with the steel pipe, piping hanger, or similar elements. If there is a need to connect copper and galvanized pipes, use dielectric connectors, keeping the elements with different materials away from contacting each other. The problem with the galvanic action can often be noticed around the water inlet and outlet when the installer is not using the dielectric connectors.

Today's new homes are mainly built with non-corrosive material (plastic), while in old houses, where the galvanized pipes are still present, or homes with wells, corrosion happens more often.

Copper pipe can also corrode, and corrosion is recognized by the blue-green stains on the pipes, tub, sink, and shower drains.

What causes corrosion

  • Low pH level of water (acidic nature of water)
  • Oxygen in water
  • Water chemistry
  • High flow rate and increased turbulence
  • Poor plumbing practices
  • Electrochemical reasons
  • Dissimilarity of the metals that are connected

Of course, there are other reasons for the rust particles in water, and it includes; water main breaks or any work/operation that has been done on the piping system outside.

Note: It is a good practice, before drinking the tap water, to let it run for some time, as it might be corrosive to some degree.

How to prevent corrosion in plumbing?

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There are several types of pipes used in home plumbing. Due to atmospheric corrosion, the black iron pipe is never used in homes but galvanized. 

Galvanization is the process of covering the iron pipes with zinc. The most popular pipe materials are copper and PEX, which are not affected by the potable water used in residential homes.

As corrosion can be a dangerous and very costly problem, prevention is vital.

Solution #1. When the elements have a protective coating, such as galvanized pipes, the air cannot get in contact with the metal surface attacking it. So, using galvanized pipes is one solution.

Solution #2. Cathodic protection, such as in the case of the anode rod, which is dissolved before other elements, is another way of protecting the vital elements of the heating system.

Solution #3. A plumbing system should be designed in a way to prevent the air from entering the system. A good example is the radiator heating system where water is rarely replaced while the same water circulates all the time.

Solution #4. Chemicals added to the system to neutralize the aggressive water effect.


As you can see from the above, corrosion is not good to any extent. Not only that it can cost you money and time, but it can affect your health and do severe damage to your home.

Corrosive water can produce staining and odors. It can reduce the water heater's energy efficiency or, even worse, damage the plumbing system and cause the premature failure of the tank, plumbing, fittings, and fixtures.

To prevent problems related to corrosion, contact the professional plumber to inspect the plumbing system and water heater and service if needed.

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