Rusty cast iron waste pipe -- and maybe a pinhole leak?


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Old 08-11-17, 02:33 PM
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Rusty cast iron waste pipe -- and maybe a pinhole leak?

What do you all think I'm looking at here? Obviously there's a fair amount of corrosion, but that little dangling blob of yucky-colored "water" that I circled... is that most likely a pinhole leak, or maybe some time of surface condensation? I wiped it off and it didn't come back right away, not that I'm sure that means anything.

In other words, is the thing rusting through?

FWIW, I have no clue about the age of the pipe. It's older than five years, but that's all I can be sure of.

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Old 08-11-17, 02:53 PM
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Take an ice pick or other sharp object and scratch and jab up in that area. If it goes in or makes the leak worse then yes... it's corroded.
 
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Old 08-11-17, 06:12 PM
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While I don't disagree that that's a viable method of determining how structurally sound it is, I probably should wait until I have suitable material for a repair, just in case it does create a bigger problem. I mean, it's the main waste drain for the house, and if I render our entire plumbing system unusable, there's a strong likelihood that my wife would kill me as I stand.

I may just drop back and punt to a plumber on this one.
 
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Old 08-12-17, 05:08 AM
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Replacing cast iron is not particularly difficult. The most difficult part is cutting or removing the damaged pipe. A reciprocating saw with a fine tooth metal cutting blade will cut the cast iron. Get several blades because they will dull quickly. Then the damaged section can be replaced using PVC pipe and no hub Fernco (rubber boot) style couplings.

Just be warned that the one leaky section may not be the only bad section. The other horizontal runs in your house may be in similar condition. If they are not leaking now they might not be far from it.
 
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Old 08-12-17, 06:06 AM
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A short-term fix is to use a rubber coupler to seal that section.

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You'd cut the rubber coupler and wrap it around the pipe and secure it.

Cast iron often corrodes from the inside out, so if you have one pinhole leak, it's just going to get worse. At some point, you'll need to replace it.
 
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Old 08-12-17, 06:15 AM
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If the circled pin-hole leak is at the bottom of the pipe, it appears that the moisture originates higher up the side where the oxidation (powdery whitish substance) begins to accumulate, forming a pattern or trail.

It looks like other patches of rust have collected at the bottom in the past, and they were not leaks at those locations . . . . just low points where the moisture eventually evaporated leaving behind the ferrous oxide residue.
 
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Old 08-12-17, 08:22 AM
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The condition of the other sections is what has me worried the most. This is the only exposed horizontal section. Beyond this, we're talking underground or in concrete, which makes inspection and replacement much more difficult.

Vermont, you do bring up a good point. I only saw two of those small "drips," but there are some much bigger corrosion blobs. So maybe it is just condensation and not a leak. Perhaps I will have to monitor it for a few days or weeks.
 
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Old 08-12-17, 11:35 AM
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Just like at the dentist looking for a cavity an ice pick can quickly determine if it's condensation or a pin hole corroded through the pipe. If it is a pin hole patch it with some chewing gum and put a Fernco rubber boot over it until you can make a permanent fix.
 
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Old 08-12-17, 01:03 PM
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I would guess the cast iron at 50+ years old with possible leaks, I would be planning in budget on replacement soon.
 
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Old 08-13-17, 01:22 PM
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Well, another "drip" has appeared. I guess I don't need to take the dentist approach. So now we go from "what is it" to "how do I fix it best?"

Certainly, I can do a small replacement section, but that only fixes one area.

I know what would have to be dug up, knocked out, etc. to replace all the cast iron in a "traditional manner." The stuff behind drywall is no problem. But I'd have about 15 feet of concrete (unknown depth) in the basement to dig up, plus maybe 40 feet to the street if we went all the way out (depending on where exactly the sewer is under the street).

Does anyone have any thoughts on the pipe relining process? There are several companies near me that offer the cured-in-place relining for residential customers.
 
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Old 08-13-17, 04:15 PM
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Pipe relining can work quite well. There are no companies in my area that do it so it's more expensive than replacement in some cases. If there is an installer in your area it may be a very good option at least for the pipes that are out of reach.
 
 

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