A water heater consists of metal in contact with water. Yet a water heater doesn\u2019t suffer from rust\u2014or at least it shouldn\u2019t until it\u2019s been in service for many years. We\u2019re going to look a bit closer at corrosion in water heaters to see the defenses that they have against rust, and how rush might eventually take hold.<\/p>\n
The main reason that a storage tank water heater doesn\u2019t normally rust is because of a part called the anode rod, or the sacrificial anode rod. This is a rod made of two different metals that goes through the center of the tank. The actual science behind how the anode rod protects the water heater is complex, but the short version is that the rod attracts oxidation that would normally affect the water tank. In other words, it rusts before the tank can rust, in essence \u201csacrificing\u201d itself.<\/p>\n
A device called the pressure expansion valve also helps prevent rust, since it allows the water in the tank to completely fill it, rather than leave open air at the top as a cushion. The presence of too much oxygen encourages rust.<\/p>\n
The principle cause of rust starting early in a water heater is the anode rod corroding all the way through. The rod must be replaced occasionally as it corrodes, and this is a job your water heater technician will take care of during routine maintenance. Scheduling maintenance each year is the best way to prevent rust from starting.<\/p>\n
Age will eventually allow corrosion to appear on a water heater, and when this happens the corroded parts can sometimes be replaced (the heat exchanger, for example). But usually when a water heater is old enough that rust is beginning to affect the tank itself, it is best to have the unit replaced.<\/p>\n