So I noticed today there's some rust spots showing up on the outside/bottom on the water heater. No more than a couple specs. Should I be worried?

  • Determine whether the rust is originating on the outside or inside. Rust forms in a somewhat "cone" shape. The deterioration will be wider on the originating side. An area of surface gets eaten away and the deepest spots break through the other side. So the other side tends to be original surface with a hole in it. Use a product like Evapo-Rust on the worst spots. If the rust is originating on the outside, you will see residual metal behind the rust, and any actual holes will be within that area. If the rust is originating on the inside, the outside will have holes in the original surface.
    – fixer1234
    Commented May 16, 2017 at 17:10

3 Answers 3


Most water heaters have an inner tank surrounded by an insulation material surrounded by the outer shell. If it is the outer shell that has some rust spots then there probably is not anything to be worried about. So depending on where the rust spots are located you may not need to worry about them at all.

But considering that you are seeing rust spots on your water heater that might mean that it is fairly old. If it is old, then you should think about replacing your water heater... a new water heater will save you a lot of money in energy costs (new ones are much more energy efficient).


Water heaters have a sacrificial rod in them -- sometimes two -- and the rod will sacrifice itself to protect the tank. This rod is supposed to be replaced every 6 years or so. If there are two rods, then probably every 10-12 years.

If the water heater is under 5 years old, or if you've been replacing the rods, then there shouldn't be any problem unless the water heater is 20+ years old.

If you haven't been replacing the rods (and are long past-due), or if the water heater is old, replacement might be necessary.


Sounds like the inner tank is potentially leaking, and leaving the outer jacket wet. Ever see what happens when a hot water heater fails? It can be catastrophic, tearing through walls and floors, or just get your floor wet. Either way, you may want to get it checked out.

  • could also just be condensation from the basement. We have a moisture problem and we need a dehumidifier.
    – Doug T.
    Commented Jan 19, 2011 at 16:16
  • 3
    That's true as well, but generally condensation occurs on something colder then the surrounding environment, not hotter. If the relative humidity is extremely high you get a relatively uniform condensation everywhere. Cold glass, hot day.. You get the idea. It might be condensate on the cold water line and running down the tank, but in general.. Hot things don't collect moisture on the outside.
    – Essobi
    Commented Jan 19, 2011 at 16:44

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