Is my cast iron pipe rusting??

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Old 02-18-18, 04:21 PM
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Is my cast iron pipe rusting??

Moved in 3 yrs ago and replaced majority of the plumbing as part of other renovations...cast iron out and new PVC in.......where I was NOT planning to do any work and didn't really look until recently is the main sewer pipe in the basement which is actually partially embedded in the concrete slab of the basement.

So what I am noticing now is that in some places...which look like previous damage from water are showing signs of something that seems like surface rust....Pictures below.... they actually seem like corrosion damaging the surface of the pipe and making a very tiny indentations....

I am not sure if cast iron could actually rust (after all water flows through it nonstop for many, many years) but I do worry a bit and wonder if this is something I need to address either by:
1; Major renovation - blast the concrete to free the pipe then replace it with PVC
2. Much smaller repair by just carefully sanding the surface, cleaning the rust and treating with corrosion inhibitor and protect it with paint.

thanks!
 
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Old 02-18-18, 05:42 PM
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I can't speak as an expert or plumber, but I doubt you have a problem with the pipe. Keep in mind it's a drain pipe with little or no pressure and it's cast iron. It takes many, many years for CI to rust or corrode through unless something deliberately attacks it.
 
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Old 02-19-18, 06:12 AM
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Cast iron pipe will fail. I had cast iron pipe under concrete basement floor which leaked after only 20 years or less.
 
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Old 02-19-18, 07:57 AM
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CI pipe does rust, and typically from the inside out. I've heard that painted CI tends to rust quicker since it doesn't breathe (not sure if it's true or not)

If the pipe is rusting on the outside, it's likely rusting through and will need to be replaced at some point in the near future.
 
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Old 02-20-18, 05:41 AM
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Wink

I feel I was misunderstood with my initial reply.

Yes, of course CI rust and corrodes.

I lifted these from other website that perhaps explains my thoughts better.

"The average lifespan of cast iron drain/sewer pipe is 50 to 65 years. It is easily recognized by the thickened female “hub” at each pipe segment connection. Rust eventually eats through cast iron, primarily from the inside out, as shown in the photo below. Because corrosion is accelerated by moisture, pipe with light effluent flow and installed in a dry environment can survive 20 to 30 years longer. Cast iron began to be replaced by plastic PVC and ABS plastic pipe in the mid 1970s, and has not been used for new construction since the 1980s."

and

"When it comes to the life expectancy of cast iron sewer pipes, several factors can cause the life expectancy to vary. For example: Cast iron piping in a commercial location will most likely have more use than a single family home. The more use, the higher the chance of decreased life expectancy. A restaurant that it is open breakfast, lunch, and dinner, will increase the chance of their cast iron drain pipes having shortened life spans, due to the high flow of water and amount of grease running through the pipes consistently."

My point being, don't look for trouble. Surface rust or corrosion does not mean imminent failure is about happen. Unless you're having clogging problems or you want to take on the expense of breaking up the concrete, I would suggest a wait and see attitude. Just how bad is the corrosion? Does it seem like the wall is paper thin? A few pitted spots may not be sufficient enough to assume leakage. It may well last another 15 to 20 years. I'm not a fan of fixing what's not broken.

Just my opinion.
 
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Old 02-20-18, 10:24 AM
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All good advice and Norm201 - I fully agree.....if not (completely) broken - this is one job, I would not want to tackle this year.

As for the water damage...I should have been clear..... it is NOT from the pipe....the water damage is probably from some old previous events, like leak from bath tub possible flooding in the basement...... The signs are there....they seem old though and probably only contributed to the current erosion of the pipe surface but to your point....those are minor nicks.... just on the surface, maybe 1/8 deep....I can feel them with my fingernails.... so it is not just paint but a bit of the pipe as well
 
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