Rusting chimney

[Jon mackay]

What would the recommendation be for an appliance chimney (water heater) that has surface rusting?

Should it be primed and painted? It is over 40 years old so I didn't think it would get a whole lot worse any time soon.

[Bob Harper]

The warranty has expired and this vent has outlived its normal service life. Replace it. Also, if this is only a WH, it is probably oversized. Otherwise, they should perform combustion analysis to ascertain if it is firing properly.

[Eric Barker]

Jon, As Bob referenced it is a vent, not a chimney. A technicality perhaps but one worth adhering to.

[Markus Keller]

That much rust I recommend replacement. When it's less rust and more like surface rust, I recommend prime and paint with approved materials for the application.