Do All Water Heaters Have Anode Rods


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Whether or not a water heater needs an anode rod is determined by style and material. Most other factors (e.g., fuel source, brand) do not affect whether or not a water heater needs an anode rod. Glass-lined steel tank-style heaters need anode rods. Stainless steel, plastic, or tankless heaters do not.

Anode rods are not an easy concept to understand logically, although it does make sense physically. A metal rod that you place in your water heater that is meant to fail and disintegrate into nothing? Anode rods play a key role in improving the lifespan of a water heater, but only certain water heaters need them.

Below I will take you through a number of different water heaters and speak about whether or not they need anode rods and why. At the end of the article, I include a table summary for quick reference and links to more detailed articles about each of the water heaters’ anode rod needs.

Not All Water Heater Need Anode Rods

An anode rod is an approximately 2 ft metal rod that extends from the top of a water heater into the body of the tank. It is made of metals such as magnesium, aluminum, and zinc, wrapped around a steel or stainless steel core.

The metals in an anode rod are meant to corrode over years of being submerged in hot water. The reason you want an anode rod to corrode is so that the walls of your tank are spared from corrosion.

There are also powdered anode rods, which use electrical impulses to intercept the corrosive elements in water.

Kohree Aluminum Zinc Anode Rod 44", Water Heater Protection Hex Head Flexible Anode Rod Includes 1 Tape Water Heaters Tank 3/4" NPT Threads for Rheem, Reliance, Richmond, Kenmore, State, GE

Certain styles of water heaters are naturally less vulnerable to corrosion than others. For example, water heaters made of stainless steel do not corrode over time and therefore do not need an anode rod. In addition, a water heater only needs an anode rod if it has a tank and is made of a material that is at risk of corrosion.

Tankless Water Heaters

Tankless water heaters do not require anode rods. They may be made in a variety of materials with varied fuel sources, but none of these varieties will require an anode rod.

Anode rods serve the purpose of sacrificing themselves to subvert the corrosive effects of water away from the water storage tank’s walls. Within a tankless water heater system, the anode rod’s job is not necessary because there is no tank present.

A tankless water heater involves pipes that draw up water and run through a heat exchange system. Water is heated directly as it goes through the pipes rather than sitting in a tank to heat up. This allows the user to draw hot water directly as needed, which makes them much more energy-efficient.

While corrosion is possible if leaking occurs within the pipe system of a tankless water heater, it is less apparent since there is not the element of sitting water.

Rheem RTEX-24 24kW 240V Electric Tankless Water Heater, Gray

State Water Heaters

State is a leading American water heater manufacturer, not a type of water heater itself. This brand has been around for about70 years and produces a variety of different types of water heaters.

Since State produces several different types of water heaters, the answer for whether State water heaters require anode rods is both yes and no. Certain types of water heaters, namely tank-style, require anode rods, while other types, namely tankless, do not require them.

State produces standard glass-lined tank-style water heaters, and this style requires an anode rod because it has a tank for storing water where corrosion will occur unless a sacrificial anode rod is present. For this reason, State’s regular tank-style water heaters require anode rods.

State also produces tankless water heaters. These do not have a storing tank where water sits and creates corrosion, so they do not require anode rods to fight corrosion. State’s tankless heaters are therefore anode-less.

Rheem Water Heaters

Rheem is another popular water heater manufacturer. They sell water heaters in a variety of styles including tank-style, tankless, and hybrid water heaters. They sell each of these styles in several variations.

Rheem has been an innovator of the hybrid water heater, introducing the style in 2009. This style blends the fast water retrieval of the tank-style water heater with the improved energy efficiency of the tankless style.

Rheem tank-style and tankless water heaters follow the same guidelines as general tank-style and tankless water heaters for if they require anode rods.

Their tank-style water heaters require anode rods to combat the effects of corrosion, except when they are made of more resistant materials.

Rheem’s Marathon tank-style water heater does not require an anode rod since the tank is made of polybutene, a plastic material that does not corrode. This water heater comes with a lifetime warranty, like other brands’ stainless steel models.

Their tankless models do not require anode rods. However, their hybrid-style water heaters require anode rods since they are designed with a holding tank for water.

Stainless Steel Water Heaters

Stainless steel is a premium material for tank-style water heaters since it resists corrosion and lasts a long time.

Stainless steel water heater tanks do not require an internal coating of glass, which makes them more lightweight and durable.

Stainless steel is made of a steel alloy that must include at least 10.5% chromium. This chromium is the source of stainless steel’s corrosion resistance since it reacts with air to create a protective barrier on the steel.

Rheem G100-200 LP Propane Universal Commercial Water Heater, 100 Gallon

Due to this resistance to corrosion, stainless steel water heaters do not require anode rods even though they do hold sitting water. The ions in the water are not at risk of corroding the metal of the tank.

Stainless steel water heaters are also highly immune to the build-up of minerals that commonly occurs within glass-lined water heaters. Since hard water exacerbates this mineral build-up, stainless steel water heaters are recommended in homes with very hard water.

Glass-lined Water Heaters

Glass-lined water heaters are the most common variety used in homes. They are the least expensive and can be powered by either gas or electricity. The standard glass-lined tank-style water heater that you find in most homes does require an anode rod to extend its lifespan.

Gas-lined water heaters consist of a holding tank that is externally made of steel and internally lined with glass. While glass does not corrode, the internal glass can and often does crack, and even hairline fractures can cause corrosion of the external tank.

Therefore, the tank needs to be protected from the corrosive effects of water with an anode rod. An anode rod is made of highly reactive metal that corrodes instead of the steel of the tank.

When two reactive metals are subjected to corrosive forces, the more reactive metal will take the brunt of the reaction and spare the less reactive metal. This means when an anode rod is spent, it needs to be replaced to continue to protect the tank.

The only alternative glass-lined model I have found is one with a heavy-duty plastic outside, rather than steel, making it completely resistant to corrosion. This alternative does not require an anode rod.

Indirect Water Heaters

Indirect water heaters are a variety of water heater that uses less energy than traditional gas or electric water heaters by involving a heat exchange system. Depending on the material it’s made of, it may or may not require an anode rod.

An indirect water heater involves a heating system with a boiler that externally heats up fluid. This fluid then circulates through pipes a system in the bottom of the water heater tank to heat the water.

Eastman 60022 60022/DET-5 2 Gallon Expansion Tank, White

Indirect water heaters have a storage tank for heating water through heat exchange. This tank requires an anode rod to fight corrosion unless it is made from stainless steel.

If the holding tank is made from stainless steel, then the indirect water heater will not require an anode rod since the material will be resistant enough to corrosion.

Gas Water Heaters

Gas water heaters sometimes require anode rods and sometimes do not. Many different types of water heaters are available in the gas-powered variety. There are tank-style and tankless gas-powered water heaters. I have not found hybrid gas-powered water heaters.

Additionally, indirect water heaters may technically use gas as the power source for the burner, but I will not include them here since they have been covered more in-depth above.

The power source is not the main factor that determines if a water heater needs an anode rod. The factors that determine whether a water heater requires an anode rod are style (whether it is tank-style or tankless) and material (if its tank is glass-lined or stainless steel).

Glass-lined tank-style gas water heaters require anode rods because the tank will face significant corrosion without a sacrificial anode rod to protect it. However, stainless steel tank-style gas water heaters do not require anode rods since stainless steel resists corrosion.

Tankless gas water heaters do not require anode rods because they are not as vulnerable to corrosion as tank-style water heaters since they do not have sitting water.

Electric Water Heaters

Electric water heaters are the alternative to gas-powered water heaters. Once again, the power source does not determine whether a water heater does or does not need an anode rod. Style and material are more important because these factors have to do with how vulnerable or resistant the unit is to corrosion.

Tank-style water heaters are highly vulnerable to corrosion unless they are made of stainless steel, and tankless water heaters are not as vulnerable to corrosion as tank-style.

Stiebel Eltron 233219 2.5 gallon, 1300W, 120V SHC 2.5 Mini-Tank Electric Water Heater

Since they are constantly holding sitting water within their tank, the standard glass-lined tank-style water heater unit requires an anode rod whether it is powered by gas or electricity. Tank-style water heaters can also come in stainless steel, which is resistant to corrosion. For this reason, stainless steel tank-style water heaters do not require an anode rod no matter the power source.

Tankless water heaters do not require anode rods, no matter the power source, since they do not hold water for a prolonged period of time within the unit.

Which Water Heaters Need Anode Rods: Table Summary

Water heaterAnode rod requiredLink to detailed article
Tankless water heaterNoView
State water heaterOnly tank-typeView
Rheem water heaterOnly tank-typeView
Stainless steel water heaterNoView
Glass-lined water heaterYesView
Indirect water heaterSometimesView
Gas water heatersSometimesView
Electric water heatersSometimesView

When you purchase a new water heater and that water heater is of a type that requires an anode rod, then you should get the first anode rod free with the heater. The type of anode rod that will work best for you will depend on the quality of your water.

Sources

http://www.westinghousewaterheating.com/literature/WH-Electric-Brochure.pdf

https://www.thyssenkrupp-materials.co.uk/does-stainless-steel-rust

https://www.energy.gov/energysaver/tankless-coil-and-indirect-water-heaters

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