Black iron pipe corrosion

I inspected a home last week that was only 10 years old with no visible or measurable moisture. The pipes had a layer of corrosion I would expect in a much older home or at least one with a wet crawlspace. I recommended a plumber evaluate. At what point should I recommend further evaluation?

Daniel Arnett
Home Resource Solutions



Really not a problem just normal corrosion , did you take a humidity reading by chance ?

No humidity tests, just a negative moisture test. No readings of moisture was present. The insulation was blackened so there was clearly moisture at some point. I had not seen that much corrosion on pipes aged less than 40-50 years old. Seemed premature. I know they were not leaking but am not sure how to determine when the corrosion is excessive. Any recommended rule of thumb on this?

Daniel Arnett WA#1596
Home Resource Solutions LLC

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Comments (12)

It probably depends where you live. My sister lives in CT, her house was built in 1890, most if not all of the black pipe is original as are the radiators. She has steam heat, which is more corrosive then water. We have a house built in 1929 with black pipe and hydronic heat. The pipe looks good as new. I’d leave it.

Like Bookmark April 29, 2010 at 10:36PM:)

First of all, the fittings are iron, the pipe is steel. The fittings will rust faster as they are generally just coated with oil. Once this oil gets wiped / dries / whatever, it rusts. The pipe is generally coated with a lacquer IF it comes from a big box store. This will deteriorate with time, moisture, heat, abrasion, any number of things.

If the steel pipe comes from a steel yard, it’s not coated with anything more than mill scale. The plumber then cuts to length and cuts their own threads, and generally saves 50-75% of the cost at Home Depot. It just rusts faster…which is the point with black “iron” pipe anyway. You want uniform rust, not the BS spot rusts that you get with galvanized. That’s why black pipe is used for natural gas and galvanized is not supposed to be used.