Cellular ABS Pipe Exposed above the roof - Is this a problem?

So I observed vent pipes which are cellular ABS. The inner cells of the pipe are exposed to weather. The vent pipes are spongie, discolored and have a lot of fine surface cracking.
For some reason I remember hearing somewhere that ABS pipe is not ok for exterior applications(Photo Degrading). Is this true?
Also If my memory serves me shouldn’t the exposed inner wall of the Cellular ABS be sealed to prevent water logging of the foam core?

Cellular core abs deteriorates due to uv exposure, the foam deteriorates, however abs wont, use the solid abs for roof vent penetrations.
There are two types of abs pipe you can buy, the cellular core, which has the foam inside two layers of real abs, and the real solid abs, the latter is which you want if you are going to experience any exposure to uv.


Thanks Marcel!

Do you think this is worth a write up?

Would you want to know if you were buying?


ABS pipe may be used in buried or above ground DWV applications. It may be used outdoors if the pipe contains pigments to shield against ultraviolet radiation, or jurisdictions may require the pipe to be painted with water-based latex paint for outdoor use. Check with the pipe supplier for details about local regulations for this material.
Since the cellular abs is affected by uv and more fragile, I would make note of it considering it is already chipped in your photo.
Typically they only use ABS going through the roof because it is black. It is not a big job to replace and some jurisdiction might not even allow the cellular core.

I just did some research and the manufacture of this pipe does not prohibit its use outdoors or at least that’s how I understood it. See page 48 at this link.

Only if it is a relevant issue in need of repair. The answer to that I hope to arrive at through this post.

Well, if your locale allows the use of foam core abs for venting, then my concern would be it being fragile. Anything (like a tree branch) hits it can easily damage it. It may not be in need of immediate repair but if that was on my house, I would definitely want to know about it so I could monitor (because it can easily break and develop a leak) or replace it for longevity. Here we use PVC.

Same around here and they paint it black.
Charlotte Pipe evens states to paint it to prevent UV degradation.
Foam core is fragile and it only takes once.


Ok its getting the write up. Thank you all for sharing your Insight & experience. I really appreciate it :smiley:

Would be easy to cut from attic and just replace the top couple feet…

This has been an approved in a DWV system for a long time. As a plumber and plumbing contractor with 33 years in the field all piping degrades from UV (PVC) or moisture (cast iron). Leave it as it you will likely damage the rubber boot removing and installing a new pipe. Just recommend painting the pipe for added protection.

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No focus on your SOP unless you have first hand experience in the plumbing industry and understand what normal age looks like on pipes. A chip on the pipe, seriously you’re going to write that up for a vent stack? You didn’t notice the shingle was in contact with the rubber boot on the right side. As a 33 year pluming veteran and contractor that would have been a bigger concern for me but what do I know. Bottom line…don’t sweat the petty things and don’t pet the sweaty things.

“Typically they only use ABS going through the roof because it is black.”

Really? Can you tell me where this is done? I’m interested to know how they transition from other DWV material to black ABS. I’d love to see a photo of this transition. Thanks for your help.

Done on new homes and usually switched from pvc to abs just below the roof. Sorry I don’t have a picture available handy.
And most often then not, it is glued.
ABS to PVC cement is only meant to connect an ABS system to a PVC system. An example of this would be an ABS drain system inside of a home connecting to a PVC drain system just outside the building, or vice-versa. That’s the only place that this cement is supposed to be used.

Just a FYI for all of our home inspectors. Transition glue from ABS to PVC is not an approved material in the Uniform Mechanical Code. Sure you can buy it at Home Depot next to those Shark Bite adapters but it doesn’t mean they are legal. I know we are not code enforcers but if you see a transition made from dissimalar plastic piping it must be made by a mechanical means. Same with cast iron to plastic unless they use an approved lead in soil adapter. If a region you live in is stubbing ABS pipe out of the roof and attaching it into PVC they are clearly in violation as you can never downgrade a code. If this is something they “typically do” they are typically in violation.

A lot of good detailed information has come out in this post. I think it’s obvious this isn’t a big fish no matter how you slice it. But I like to understand how things work so when my clients ask me questions I’m able to answer them thoroughly. So I’m glad these differing opinions are coming out.
This particular pipe coming through the roof is not in good shape. I squeeze the pipe the pipe readily deformed like it was made out of cardboard felt nothing like the same pipe that is on the other side of the roof. I don’t think this pipe will be a problem for quite a while but it certainly isn’t going to last as I would expect a vent pipe should. This stuff is largely not even available anymore around here everyone seems to prefer PVC despite it costing more. I only see it in homes from the 70s and 80s. I did run into a plumber on a project out in PA who was still using it. I wasted no time insulting him for using that garbage all in good fun though. We would always use rubber no hub connectors to connect ABS to PVC or cast iron. As for the underground connection to the Sewer lateral line the building departments I have worked with did not seem to care about the connection method so long as it was encased in concrete at the union.

Well, maybe you can come up here and tell that to the AHJ. LOL
I don’t think the house is going to fall down because of a 3’ abs pipe on pvc for a vent and I don’t think the sh_t is going to care either, as long as it flows down hill. LOL

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