Anode rods typically come in three varieties, made up of three different types of metals: magnesium, aluminum, and zinc. The magnesium anode rod is the most common type of anode rod. The magnesium rods are best used in areas with soft water as they corrode easily. The second most common type is the aluminum anode rod.
Selecting your new anode rod should be based on your water's condition and your budget. For example, to get rid of bacteria causing your water to smell foul, go with a zinc/aluminum or electric anode rod. For the most economical choice, magnesium is the way to go – but be ready to replace it again in a few short years.
The magnesium anode offers better protection and is recommended. In some water conditions, the magnesium anode dissolves too rapidly; in that case the aluminum is a longer lasting (but not as protective) replacement.
Material Composition: The choice between aluminum, magnesium, and zinc for anode rods depends on water composition and personal preference. Aluminum rods are durable and ideal for hard water areas but may not be suitable for homes with softened water due to their slower reaction rate.
To identify which anode rode you have simply look at the face of the brass nut on the anode, if you see an “A” stamped into the front of the brass nut you have an aluminum anode, if the face of the nut is blank you have a magnesium anode.
Very often, replacing the standard magnesium or aluminum anode rod with an aluminum/zinc alloy anode will solve the problem. The zinc is a key ingredient, since pure aluminum anodes will also reek to high heaven.
Weight: Aluminium is significantly lighter than zinc, by a factor of 2.5. Al anodes are lighter to ship and to fit. Capacity: The electrochemical capacity is more than 3 times higher than of the same mass of zinc (you can protect more with less). See data sheet for aluminium alloyed sacrificial anodes.
Magnesium Anode Rods
Acting as a sacrificial metal, they extend the lifespan of your equipment by preventing rust and ensuring optimal performance. Designed for durability and efficiency, anode rods are an essential investment in system maintenance and reliability.
The lower the measured voltage, the less likely the metal will corrode. This is where zinc anodes have a problem protecting aluminum components. Zinc anodes sit at -1.05V and aluminum components sit at around -0.75V, a difference of 0.3V, not much more than the required 0.2V drop.
Anode rods require routine inspection and replacement, approximately every three to five years. Without proper maintenance, the anode rod loses its ability to divert damaging particulates from your tank and can accelerate rust and corrosion from chemical reactions, excessive heat, and imbalanced pH levels.
You'll spend between $20 and $50 on the rod. If you choose to hire a water heater pro to get the job done, an anode rod replacement will cost you between $200 and $300. If you're not sure whether to handle this repair yourself, first examine your water heater.
The three main water types are salt, fresh, and brackish, a combination of the two. Zinc anodes only protect in salt water. Aluminum anodes protect very well in salt and brackish waters. Magnesium anodes are designed for fresh water use only, never in salt water.
Best Anode Rod for Residential Water Heaters
The choice between aluminum or magnesium anode rods for residential water heaters depends on the local water quality. Magnesium rods are better for areas with soft water, while aluminum rods are ideal for hard water areas.
The anode rod attracts corrosive elements, such as oxygen and hydrogen sulfide, which would otherwise corrode the walls of your hot water tank.
The RV anode rod's size and material type: aluminum/zinc anode rod, 9.25" long, ¾" threads, uses a 1-1/16'' socket. The RV Aluminum/Zinc anode rod fits for almost all water heaters including; A.O. smith, Rheem, Reliance, Richmond, Kenmore, State, GE and many more that also use the standard ¾" NPT Anode Rod Connection.
Aluminum anodes are lighter, cheaper, and more eco-friendly, but they need regular cleaning to avoid passivation. Zinc anodes are heavier, more expensive, and more toxic, but they are more reliable in salt water.
They will not work! Do not mix anode types - aluminum anodes will try to protect zinc anodes on the same bonding circuit.
By replacing your anode rod every 3-5 years, your water heater can last well over 20 years without any risk of leaks and resulting water damage. Unfortunately, if you ignore this important water heater maintenance task, you may need to replace the entire water heater after only 10 years of use.
Water hardness: Magnesium anode rods are more effective in soft water, while aluminum anode rods are more effective in hard water. This is because magnesium anode rods will corrode faster in hard water, which means that they will need to be replaced more frequently.
For example, a corroded aluminum or magnesium sacrificial anode rod is a common cause behind water having a rotten-egg smell.
Of the three, zinc is the most expensive, both in terms of material and installation costs. This can mean that on projects where budgets are restricted zinc can prove cost prohibitive. Aluminium is less expensive, but steel is by far the most cost-effective option due to the price of the material.
Recommendations. As mentioned earlier, I recommend installing two 17 pound magnesium anodes on a 1,000 gallon tank. The reason I recommend two is to ensure that enough cathodic protection current is available for many years.