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Best Anode Rod for Hard Water


Due to their low reactivity, aluminum rods are the best sacrificial rods for hard water. However, the overall best is a powered rod. Both types can handle the high mineral content, though powered rods usually provide better protection against corrosion, limescale buildup, and smell.

Different types of anode rods come with various strengths and weaknesses. If you’re not already familiar with them, it can be hard to know what type of rod works best with what type of water.

If you have hard water in your home, reading through this article should help you make an informed decision on which rod is going to last the longest, provide the best protection for your water heater, and better suit your needs!

Hard Water Is Very Corrosive

Hard water gains its name from the type of minerals it contains. Hard water, in comparison to soft water, has a higher pH level and contains a higher concentration of minerals, primarily calcium and magnesium, though others may be present.

In other words, the fewer minerals are in the water, the softer it is.

Even though hard water has a lower corrosion rate than soft water, it doesn’t mean that it doesn’t cause corrosion at all. It just does so in a different way.

The minerals can also build up on various surfaces over time. This increases the tendency of the tank to corrode since mineral buildup on the inside of water tanks can wear away at the top layer of the steel, making it much more prone to rust.

Hard Water Causes Limescale

Limescale, as mentioned, is a buildup of minerals, primarily calcium carbonate. Once the water evaporates, it leaves behind the minerals it contains, allowing them to build up over time and form a hard, thick layer of deposit.  

hard water causes limescale buildup

Since hard water contains higher concentrations of minerals, the harder the water, the faster it creates limescale buildup.

Limescale is not harmful to our health, but as it develops, it can become a problem. This is especially true for appliances like water heaters.

Over time, limescale buildup will surround a water heater’s heating element. This forces it to warm through the limescale in order to heat the water, making it work harder and less efficiently to do its job. This can reduce the heater’s lifespan by several years.

There Are Several Types of Anode Rods

There are two primary categories of anode rods. The first is a powered or non-sacrificial anode rod, and the second is a sacrificial rod.

A powered rod is meant to last for the entire lifespan of your water heater. It keeps corrosion at bay by using electrical pulses to prevent corrosion and limescale buildup inside the tank.

Sacrificial anode rods, on the other hand, are thus named because they draw corrosive elements towards themselves. They break down in place of your tank, literally “sacrificing” themselves and requiring replacement every few years.

a man holding a sacrificial anode rod damaged from corrosion

Sacrificial rods can be made from various types of metal, like magnesium, aluminum, or a combination of zinc and aluminum. Because of this, they are differently equipped to handle different water conditions.

Comparing Their Performance in Hard Water

Magnesium Anode Rods

Magnesium is very reactive to the minerals found in hard water. This means that a magnesium anode rod will corrode much faster than an anode of other material once submerged in hard water.

For this reason, magnesium anodes work best in soft or softened water.

Aluminum Anode Rods

Aluminum is not as reactive as magnesium is. This allows aluminum anode rods to last for a longer time in hard-water environments while still maintaining a higher reactiveness to corrosive materials than the steel of the tank does. 

Aluminum anode rods are therefore much better suited to hard conditions.

Zinc Anode Rods

Zinc anodes are actually composed of both zinc and aluminum and are typically used for smelly water, where the smell is caused by bacteria. 

The zinc to aluminum ratio is usually 1:10, meaning they are primarily aluminum. They work well in hard water because of this.

Powered Anode Rods

The actual rod portion of a powered anode is made of titanium, a material highly resistant to corrosion. When in use, a small electrical current is sent through the rod.

illustration of powered anode rod

The current scatters minerals and harmful electrons within the water, preventing any type of buildup on the walls of the water heater and therefore keeping corrosion and limescale at bay even when used in hard water.

Is Powered or Aluminum Anode Rod Better?

When it comes down to handling hard water, your best options are aluminum or powered anodes. Both will be able to do the job, albeit in different ways.

Which one is better will ultimately differ from case to case, although powered anode rods seem to provide more well-rounded protection for the water heater tank.

In order to decide which one will better suit your needs and your home, let’s take a more in-depth look at each.

Aluminum Anode Rod Overview

Aluminum rods are, as discussed, not highly reactive anodes. This is what allows them to last longer than magnesium anodes in hard water conditions, where many minerals are present.

That said, they come with their own set of drawbacks as well as benefits. For one, they are very cheap. They can often be found for only about $20- $40, like this Camco Aluminum Anode Rod (amazon link).

However, they still need to be replaced every few years. Additionally, the mineral buildup that will likely occur with an aluminum rod may eventually clog plumbing or reduce the heater’s efficiency.

Pros and Cons Table

ProsCons
Cheapest anode rod ($20-40).Needs replacement every 3-5 years.
Lowest reactivity of sacrificial rods increases lifespan.Low reactivity does not fully prevent corrosion.
Low reactivity allows function in hard water.Buildup can break off and clog plumbing.
Can prevent smelly water (only if the anode also contains zinc).

Powered Anode Rods Overview

Powered anode rods are rather unique, as they are non-sacrificial. The most popular brand on the market right now is the Corro-Protec (amazon link).

Corro-Protec™ Powered Anode Rod for Water Heater, 20-Year Warranty, Eliminates Rotten Egg/Sulfur Smell within 24 hours, Stops Corrosion and Reduces Limescale, Electrical Anode Rod Made of Titanium

Powered anode rods are beneficial in that they are meant to last for your tank’s entire lifespan without replacement. This does make them much more expensive than sacrificial rods upfront but their operating costs are extremely low, and they may save you money in the long run.

The fact that they run on electricity is what allows them to handle limescale, corrosion, and smelly water, but if the power ever goes out for a prolonged period, then you’re going to be without a functional anode for that time.

Pros and Cons Table

ProsCons
Built to last for decades without replacement.Expensive cost up front ($100-200).
Will not corrode.Requires electricity to run.
Automatically adjusts to work in both hard and soft water.Needs an outlet near the water heater.
Can prevent smelly water.

Sources

https://www.brothersplumbing.ca/blog/limescale-prevention/how-to-remove-limescale-and-prevent-it-from-coming-back/

https://foodservice.winstonind.com/blog/say-no-to-rusty-stainless-steel/

https://gregknowswater.com/soft-water-not-for-drinking-is-softened-water-corrosive/

https://www.hustedplumbing.com/blog/water-heater-service/hard-water-water-heater-bad-news/

https://kylesgarage.com/powered-anode-rod-vs-sacrificial-anode-rod/

https://www.landmarkhw.com/resources/plumbing/the-difference-between-hard-and-soft-water/2/21

http://region8water.colostate.edu/PDFs/Well%20Educated/Revised%20Fact%20Sheets%20-%20Nov%202012/Corrosivity%20&%20Hardness%202012-11-27.pdf

https://www.researchgate.net/publication/292138538_COMPARISON_OF_CORROSION_CHARACTERISTICS_OF_CARBON_STEEL_IN_SOFT_AND_HARD_WATERS_UNDER_DIFFERENT_PARAMETERS

https://ukwta.org/assets/NewFolder/Softened-water-is-not-more-corrosive-Rev2-1.pdf

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