Why replace an anode?

Anode Old NewWater heaters fail because of rust and the sacrificial anode is the component that prevents the tank from rusting. Timely replacement of the anode in your hot water tank can triple its life.

So, what is an anode?

An anode is an alloy rod suspended in the water inside the heater tank. Corrosion attacks the alloy before the steel walls of the tank. Hence the term “sacrificial”.

In the photo you can see the old anode on the Left. The alloy is almost completely eroded away leaving the mild steel core. The replacement anode beside it is yet to have the same fate. Better the anode than your tank!

Tank corrosion is the main cause of hot water unit failure. The life expectancy of the originally installed anode is what determines the length of the manufacturer warranty. Therefore replacing the anode extends its life.

Timely replacement of the anode in your hot water tank can triple its life! 

Replacing the anode every 4 to 8 years ensures full corrosion protection is maintained.

Why is an anode necessary?

The glass lining of the tank is not sufficient to totally prevent corrosion. The glazing material is quite brittle and the continuous expansion and contraction of the tank every time the water is heated causes the development of thousands of hairline cracks. As these cracks appear, the steel walls on the inside of the tank are exposed to the effects of corrosion. The alloy anode reacts with this exposed steel, sacrificially corroding before the steel.

All manufacturers of glass-lined, steel water heaters use anodes to protect them against rust! Of special interest is the fact that their 10 year guarantee models are fitted with heavy duty anodes or twin anodes for extra protection. The replacement interval varies, depending on the size of the heater, the quality of the water and level of use.

Tank corrosion is the main cause of hot water unit failure!

This principle of corrosion protection is nothing new. No experienced boat owner would risk his investment when all it requires to prevent corrosion is to keep an effective sacrificial anode in the appropriate place.

propeller anodeSacrificial anodes on the hull of a boat




The white 'eggs' in the photo are sacrificial anodes
to prevent corrosion


The same system is used on all commercial shipping, oil drilling platforms as well as underground pipelines and storage tanks. It’s far more economical to replace the anode than to allow the vessel itself to corrode. This same logic also applies to domestic water heaters.


For more information see an article about sacrificial anodes on Wikipedia, the free encyclopedia website.