How Does a Water Heater Keep from Rusting?

turning down your water heater temperature

It’s likely that you already understand, when water meets metal, there’s a high chance of corrosion occurring. Corrosion is the term used to describe the chemical reaction between water and metal in the presence of oxygen, a process we know as rusting. This type of damage can quickly ruin many types of appliances and equipment as it weakens the metal and that metal starts to rust and break away.

So what about your home’s water heater? It is, after all, primarily made of metal, and it stores and circulates water. So why doesn’t it start rusting? Well, corrosion is rare in water heaters, and usually only starts late in the system’s life, if not for the following protective measures inherent with the system setup.

The Lining of the Tank

Your water heater’s tank is typically made of a very durable steel. However, the inside lining is made of glass, which does not corrode. It is possible for cracks in the glass to allow water to reach the metal, which would in fact lead to rusting, as well as water leaks.

Absence of Air within the Tank

Historically, water heaters were designed in a way that they kept a cushion of air at the top of the tank to prevent water pressure spikes. However, enabling air to be in the tank allowed for corrosion to start. Now, water heaters include no air from the tank, and instead use an expansion tank placed over the main one to absorb the water pressure increase.

The Sacrificial Anode Rod

Actually, it’s just called an anode rod, but it is, in nature, sacrificial. Their presence alone prevents corrosion and rust from rapidly ruining your water heater tank. Also referred to as a cathodic anode rod, this component runs the length of the center of your water heater tank. It’s comprised of two different pieces of metal that attract the oxidation ions that cause corrosion. Essentially, an anode rod corrodes in order to save the rest of the system from doing so, thus its “sacrificial” nickname.

Eventually, the anode rod in your water heater tank will corrode completely and will need to be replaced. This is where water heater maintenance comes in—the anode rod is among many components that our technicians check on during your maintenance session. You can also have a plumber show you how to check the anode rod yourself to see if it requires replacement yet, however do keep in mind that it takes a pro to put in a new one—we want to make sure you have the correct type for your water heater.

“What If My Water Heater Rusts Anyway?”

No matter how well-maintained your water heater is, or how many times you replace the anode rod, your water heater can start to corrode and rust once it hits a certain age—typically after 15 years of service. It might not actually be from the water but rather form the combustion of gases from the burner. But whatever the cause, when corrosion starts to impact your water heater, it’s time to look into a replacement system.

Contact Aurora Plumbing Company for professional plumbing in Littleton, CO. We have someone in your neighborhood today!


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