Rigid Magnesium Water Heater Anode Rod

One of the most commonly found factors limiting the life of water heaters is interior corrosion. The water inside the heater tank can be very harmful to the system as the harsh minerals it contains can build up and eat away at the steel surfaces, a process which is only worsened by the high water temperatures.

Known as soft water anodes, magnesium pencil anode rods are an excellent anode to protect the inside metal surface of the water heater tank from rust by electro-chemical action. The sacrificial magnesium rod (the anodes) corrodes in place of the tank (the cathode). The lifetime of a water heater can be greatly extended when the anode rods are replaced at regular intervals.

Water heater anode rods are typically made of either aluminum, magnesium or zinc. Magnesium anode rods tend to be consumed quicker than aluminum or zinc anode rods due to the higher voltage they create during the sacrificial process. Despite this, magnesium anodes are an increasingly popular choice as dissolved magnesium in water can offer many health benefits.




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Quality Substrate Material
Constructed of high-grade magnesium, our pencil anode rod is manufactured according to ASTM B843-AZ31B standard. The magnesium alloy contains Al, Zn and Mn elements, while the content of Ni, Fe and Cu must be kept as low as possible.

Element ASTM B843 – AZ31B
Aluminum (Al) 2.5 ~ 3.5%
Zinc (Zn) 0.6 ~ 1.4%
Manganese (Mn) 0.2 ~ 1.0%
Silicon (Si) 0.1% Max
Iron (Fe) 0.005% Max
Copper (Cu) 0.01% Max
Cadmium (Cd) 0.04% Max
Nickel (Ni) 0.001% Max
Total Impurities 0.3% Max
Magnesium (Mg) Remainder

High Current Output
This extruded magnesium anode rod has high surface and length ratios in relation to cross-sectional area, this allows a greater current per weight than typical cast anodes. By supplying stronger current, our magnesium pencil anode rod can deliver effective protection to water heaters, even in higher resistivity electrolytes.

Uniform Current Distribution
With a thin steel core running the entire length of the anode as a support, the magnesium pencil anode rod provides a uniform and efficient current distribution to ensure stable performance.

Easy Replacement
The anode rod is easily replaceable and should be checked each time the water heater tank is drained. Generally, anode rods should be replaced when the corrosion has consumed approximately 75% of the rod’s mass. Our pencil anode rod is expected to provide up to two years of corrosion protection.

Strict Quality Control
By conforming to ISO 9001:2015 standards, our magnesium anode rods are manufactured, inspected, and tested in accordance with our stringent quality control procedures to ensure peak performance.

Customized Configurations
Standard sizes below are available at Jennings Anodes warehouse. Other sizes are available upon request.

Item No. Rod Diameter Rod Diameter NPT
JA-WHR-M12 Ø0.5″ (Ø12.7 mm) Ø0.13″ (Ø3.4 mm) 1/2”
JA-WHR-M17 Ø0.67″ (Ø17 mm) Ø0.13″ (Ø3.4 mm) 3/4”
JA-WHR-M21 Ø0.84″ (Ø21.3 mm) Ø0.13″ (Ø3.4 mm) 3/4”
JA-WHR-M22 Ø0.9″ (Ø22.9 mm) Ø0.13″ (Ø3.4 mm) 3/4”

Main Technical Parameters





Core Wire Diameter

3.4 mm


Fresh Water


Water Heater

Design Life

2 years

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