Anode rods are usually found in the center of water heater tanks and are supposed to be replaced every few years. This is an absolute pest of a task, particularly when the rods seize or break off. I think anyone who has had to replace an anode rod has researched water heaters that don’t require one.
When purchasing an electric water heater, your options are about as varied as they can get for this appliance, and not all options need an anode rod.
Electric water heaters with steel water storage tanks have anode rods. These are needed for the continued functioning of the heater as they corrode instead of the tank. If the electric water heater tank is stainless steel, the unit won’t have an anode rod. Tankless electric water heaters don’t have anode rods.
Anode Rods Important to Tank-Style Heaters
Traditional water heaters, i.e., ones that have water storage tanks, are rather expensive. They are not an appliance that you would want to replace every five or so years. You want them to last to their full potential, which can be up to 20 years!
There is a big IF when it comes to realizing the extended lifetime of a tank-style water heater, including electrically-powered models. Water heaters can last up to 20 years if anode rods are installed and replaced at appropriate intervals.
Now, from this statement, it is easy to assume that anode rods are vital to the function of water heaters, but this is not an accurate assumption. Water heaters function perfectly well without anode rods. But tank-style models only function in this way for a limited time if there is no anode rod.
So, a more accurate assumption would be that anode rods are important to the continued functioning of water heaters with storage tanks.
Let’s talk about why this is.
Why Water Heaters Need Protection
Many electric water heaters (I am tempted to say most) have steel, glass-lined water storage tanks. If you did high school science, then you know that metal and water are a bad combination.
In the presence of water, metal oxidizes to produce more stable metal compounds. However, although these are more stable chemically, they are physically less strong and degrade quickly. Furthermore, there are minerals and acidic substances in water that can corrode and weaken the metal.
The glass lining on these steel tanks acts as a physical barrier between the water and the metal shell, but the glass can become cracked or otherwise damaged, allowing water to leak through and come into contact with the steel.
Anode rods are also titled sacrificial anodes, and this is because their role in a water heater is to corrode instead of the water heater. But how is this controlled?
How Do Anode Rods Protect Your Heater?
The sacrificial function of anode rods relies on a concept known as galvanic corrosion, which “is an electrochemical process in which one metal corrodes preferentially when it is in electrical contact with another, in the presence of an electrolyte”.
In simple words, by installing the anode rod in contact with the metal of the water heater, they are considered to be in electrical contact. Anode rods are made of metals that are more reactive and, therefore, more likely to corrode than the steel of the water tank. The result is preferential corrosion of the anode.
The nature of an anode rod means that it breaks down, so for the water heater to remain protected, you have to replace your anode rod on a regular basis. This is a pain in the neck, but it is certainly cheaper to replace an anode rod every five years than to replace the whole water heater at these intervals!
Source of Heat Makes No Difference
Up ’til now, we have been mostly talking in a generalized way, but you want to know about electric water heaters in particular. Well, the truth is that the source of heat makes no difference to the necessity of an anode rod.
Whether the water is heated by an electrical element, a gas burner, or indirectly, if there is a water storage tank, then an anode rod is required.
Heat catalyzes corrosion by adding energy to the chemical reaction, but once again, the source of this heat does not make any significant impact and will not dictate how long anode rods last in water heaters.
Exception: Stainless Steel Electrical Water Heater
For the purposes of the above discussion, it was much simpler for me to say that all tank-style water heaters require anode rods, but, as with almost everything in this life, there is an exception. This is when the water storage tank is made from stainless steel.
In a paradox of chemistry, stainless steel is unreactive because part of it is so reactive.
Regular steel is mostly iron with a bit of carbon mixed in to provide additional strength. Iron is very corrosive and the product of this corrosion, iron oxide (rust), is a weak, crumbly material.
Stainless steel is still an iron alloy, but it has the benefit of the addition of chromium. Chromium is extremely reactive with oxygen. However, the resultant chromium oxide is very stable and strong and it acts as a protective barrier to prevent further corrosion of the metal alloy.
If you are a little concerned about the reliability of this chemistry, just know that this very same principle is what makes stainless steel biocompatible and safe to use as medical implants.
So, if your electric water heater tank is made from stainless steel (and you will know it is because the benefits of this metal are reflected in the price tag), then you will not need to install or replace an anode rod.
People living in regions with harsher water prefer stainless steel over steel electrical water heaters.
Electric (or Powered) Anode Rods
Suppose you have a tank-style electric water heater but you are tired of changing the anode rod, or you are looking to buy a new water heater, and electric would be the best option if only you could reduce the maintenance a little. In these cases, you should investigate powered anode rods.
Powered, or electric, anode rods are not self-sacrificing. They are typically made from titanium, which is unreactive by nature. So, if it does not sacrifice itself to corrosion, how do powered anode rods work?
Well, they are wired to an electrical source to produce electric pulses that spread through the water in the tank. Corrosion is dependent on an exchange of electrons, which are negatively charged. The pulsing current from the electric anode rod helps to keep these electrons away from the lining of your water heater tank.
Powered anodes are more costly than regular anode rods, but they have a longer lifespan because they are not going to be eaten away. Furthermore, they are an ideal option for people with well water who struggle with a rotting egg smell.
Tankless Electric Water Heaters
All tankless water heaters, electric or otherwise, do not need anode rods because there is no tank to protect and no stored water to pose a threat.