Corrosion and Water Heaters: What You Need to Know

corroded water heater

When it comes to water heaters, corrosion is a problem that can range in severity. In some instances, replacing a single component can solve the issue, while in others, the wisest option is a complete unit replacement.

To help folks get a better understanding of the relationship between corrosion and water heaters, we’ve answered the following questions below:

  • What is corrosion?

  • How do water heaters resist corrosion?

  • Why do water heaters develop corrosion?

  • Do I need to replace my water heater if part of it has corroded?

What Is Corrosion?

Encyclopedia Britannica defines corrosion as “wearing away due to chemical reactions, mainly oxidation.” We’re most familiar with corrosion occurring when a gas (like oxygen) or a liquid (like water) interacts with a metal surface to produce a corrosion product, like rust on iron or patina on copper. Encyclopedia Britannica also states that warm temperatures can accelerate the corrosion process.

When you consider that a tank-type water heater contains water as well as oxygen and has the sole purpose of heating up water to a warm temperature, you might wonder what keeps the unit from corroding away in a matter of months. Fortunately, water heaters have design features to resist that harsh, chemical process.

How Do Water Heaters Resist Corrosion?

Tank-type water heaters have three features that help them resist corrosion.

  • The interior of the water storage tank is lined with glass.

  • On top of the tank, there is a pressure relief valve. This valve maintains a necessary air cushion to prevent water pressure spikes but also keeps air from entering the tank.

  • A metal stick called the sacrificial anode rod takes on the role of corroding so that the rest of the tank won’t.

How does the sacrificial anode rod work? Time for a little chemistry lesson (we promise, it’s pretty basic)! The anode rod is usually made of aluminum or magnesium around a steel core wire. Aluminum and magnesium are “less-noble” metals, which means that they corrode in water relatively quickly.

When you place the anode rod in your water heater, it attracts all of the gases and other minerals in the water that would otherwise corrode your tank. By drawing these elements to it, the rod becomes the thing that gets corroded instead of your tank’s interior, which is why it’s dubbed the “sacrificial” anode rod.” From time to time, you may need to replace this rod when it no longer works effectively.

Why Do Water Heaters Develop Corrosion?

Despite their defenses, water heaters (both tank-type and tankless) can succumb to corrosion. In tank-type water heaters, this can be just another symptom of old age. It can also be a consequence of failing to replace a sacrificial anode rod that has been eaten away past the point of usefulness.

Tankless water heaters typically are not as likely to corrode as tank-type units because they don’t store water. However, if water leaks onto the burners, a tankless model can have corrosion issues, such as decreased efficiency due to rust buildup around the burners.

Do I Need to Replace My Water Heater If Part of It Has Corroded?

Whether you’ll need to repair or replace the unit usually depends on your water heater’s age and where the corrosion has taken place. For instance, if corrosion is only affecting one or two components, such as the burners or heat exchanger, you can usually just get these parts replaced with buying a completely new water heater.

However, if your tank’s interior or exterior has started to corrode, it’s probably in your best interest to replace the whole unit, especially if it is older than 15 years. Corrosion weakens your tank’s walls, making them more susceptible to developing leaks, and unfortunately, once corrosion has started, there isn’t much a technician can do to reverse it.

At Pioneer Plumbing and Septic, our team of friendly plumbers are ready to help! Call us at (281) 815-2772 to schedule same-day water heater services in Houston! Our team also serves Crosby, TX.

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