It’s a simple fact of nature. When metal sits in water it rusts and will eventually corrode down to nothing.

This could spell doom for water heaters and their steel interiors, but doesn’t thanks to the presence of anode rods, which are also known as sacrificial anodes. These simple but ingenuous devices “throw themselves on the sword” so that water heaters can survive and keep running for years.

What are Sacrificial Anode Rods and How Do They Work?

Sacrificial anodes are long cylinders of aluminum or magnesium attached to a steel wire core. While it is true that all metals rust in water, different metals corrode at varying rates and that is what helps sacrificial anodes protect the steel interiors of water heater tanks.

Aluminum and magnesium are more reactive than steel, which is why anodes made from them will rust away completely before any corrosion occurs in the tank. As long as anode rods are replaced on a regular basis (once six inches of the core wire have been exposed by corrosion a new one is needed) the lifespan of a water heater tank can be extended indefinitely.

Some sacrificial anodes are screwed into the top section of water heater tanks while others are inserted through hot-water outlets as part of a larger pipe assembly. Water heaters manufactured for home use often include one of each type, both manufactured from the same metal to ensure proper functioning.

Powered Water Heater Anodes

If used in conjunction with soft water sacrificial anodes will decay much faster than normal and may need to be replaced frequently, possibly every six months if the water is extremely soft. The best alternative to avoid this complication is a powered anode, which is connected to an electrical outlet and works to stave off rusting inside water heaters by emitting a small, continuous electric current.

Powered anodes are also recommended when odor-causing bacteria infect a water heater tank and send noxious fumes running up water pipes, although special sacrificial anodes made from zinc and aluminum are also effective at counteracting this particular problem.

While sacrificial anodes cost between $45 and $75, powered anodes generally carry a price tag somewhere north of $200. Of course a powered anode does not need to be replaced every one-to-three years the way the typical sacrificial anode does, so when odor problems and soft water are ongoing concerns they’re probably worth the investment.

Check Your Water Heater Anodes Early and Often

Checking sacrificial anodes for damage is easy and can be done without the assistance of a plumber. A ratchet wrench is all that’s needed to remove them, and if excessive wearing is discovered compatible replacements for specific water heaters can be purchased from any plumbing supplier.

It’s probably a good idea to check them at least once every year, and if this is something you’ve never done before you should do it as soon as possible to make sure your anodes are still in working condition. If you’re not sure how to find them check your water heater owner’s manual for further information.

Remember, if six inches of steel core wire or more have been exposed by corrosion your sacrificial anodes will need to be replaced.

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