The Role of Magnesium Rods in the Heat Pump of the Water Heater

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  • Date:2022/02/16


What is a magnesium rod?

Magnesium rod is the common name of magnesium anode, also known as anode magnesium block, which is used to prevent corrosion of metal liner and soften water quality. In the use of Taigang type or manganese steel metal liner, the principle of electrochemical anti-corrosion sacrificial anode protection of metal in water is used to protect the cathode, the magnesium rod is used as the anode, and the metal liner is used as the cathode. In this way, a galvanic cell is formed by a conductive aqueous medium between the cathode and the anode. The battery's anode, the magnesium rod, is consumed by corrosion, while the cathode, the metallic inner conductor, is protected.


What is the role of magnesium rods?

Tap water is very easy to produce scale after heating. The scale has a certain corrosive ability. After a long time, it will be lined and cause the water heater to leak. In a water heater, magnesium rods first combine with carbonate ions in the water; bicarbonate ions combine to produce magnesium carbonate (scale).

In the water heater, the magnesium rod is installed in the middle of the metal liner. When the enamel coating on the surface of the metal liner is complete, the enamel shields the metal liner, the insulation resistance between the magnesium rod and the metal liner can reach more than 2MΩ, and the anode output current of the magnesium rod is almost zero. However, when cracks appear in the enamel liner, a small resistance is formed between the magnesium anode and the metal liner through water, and the magnesium anode starts to output current, which flows to the exposed metal liner to produce a polarized film, which repairs the damage. The enamel, which insulates the inner tank of Jinyu, prevents corrosion. Because the magnesium anode consumes itself when outputting current, it is called the sacrificial anode method.

The function of the magnesium rod will consume the negative ions in the water, and the inner tank will not be easily corroded and leaked. All magnesium rods are consumables and need to be replaced every once in a while.


How to replace the magnesium rod?

  • 1: Turn off the power and water
  • You should always turn off the circuit breaker or turn off the thermostat on gas models before doing any work on the water heater


  • 2: Find the anode rod
  • The anode rod will be at the top of the unit. In some cases it may be connected directly to the hot water outlet line on top of the heater. If you have the owner's manual for your water heater it will contain a diagram showing the anode rod location, otherwise consult the manufacturer's website


  • 3: Drain some water from the tank
  • Extend the hose to an outside location below the tank or pipe the drain. Drain only about 10% of the water from the tank. If you have a side mounted anode rod, you will need to drain more water.


  • 4: Remove the anode rod
  • The anode rod can be removed with a socket wrench or socket. If you can't turn it with a wrench, use a socket and breaker lever. Tightening the anode rod slightly will help loosen the threads and make removal easier.
  • Never use penetrating liquids such as liquid wrenches on water heater components as these may contaminate your hot water supply


  • 5: Install the new anode rod
  • If you have limited clearance, you may want to buy flexible anode rods. With the threads on the new anode rods facing down, wrap them with plumber's tape or lightly cover them with joint compound.
  • Insert the new rod or, if not replacing, the old rod. Turn the assembly clockwise until it cannot be turned by hand, then use a socket wrench to tighten it an additional 1/2 turn. Do not allow the water heater to turn or twist while doing this


  • 6: Restoring water and electricity
  • Make sure the drain is closed, then turn on the cold water supply. Open the same hot water valve as you empty the tank and let it flow until all the air in the tank is expelled 


How often should magnesium rods be replaced?

The magnesium rod should be replaced every 2-3 years of use. If it is in an area with poor water quality, it is best to replace it every 2 years. Because the water quality is poor, the magnesium rod will be consumed faster. Once consumed, it cannot be prevented. The scale problem in the water heater will also affect the heating efficiency. Therefore, the magnesium rods can be inspected regularly. If it is found that the consumption is almost equal, the after-sales personnel should be contacted for replacement in time.


Where can magnesium rods be purchased?

You can easily find replacement anode rods for standard water heater models at a hardware store or supermarket. Aluminum anode rods are the most common type, and their average price ranges from $20 to $40. Be sure to note your water heater model and tank size before buying anode rods.





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