# PVC flue pipe



## Team BP

We put in these two boilers two years ago and it's pretty obvious which one is the exhaust. The inside looks the same. This is why I do all my flues in schedule 80 cpvc. I'm just wondering what you guys have experienced.


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## AlbacoreShuffle

Thats a little to close to a window for my liking.


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## rjbphd

Team BP said:


> We put in these two boilers two years ago and it's pretty obvious which one is the exhaust. The inside looks the same. This is why I do all my flues in schedule 80 cpvc. I'm just wondering what you guys have experienced.


Not allowed per instruction manuel... and why are the pipes discolored???


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## Plumber patt

Love how the guy is asking for advice and the first two responses are shear criticism on his work


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## plbgbiz

Team BP said:


> We put in these two boilers two years ago and it's pretty obvious which one is the exhaust. The inside looks the same. This is why I do all my flues in schedule 80 cpvc. I'm just wondering what you guys have experienced.


Is the discoloration what you are asking about?

Is there a significant temperature differential between the different pipes?


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## Team BP

You only gotta be a foot from any window that opens but that's beside the point. What I'm asking is has anyone seen PVC flue pipe become discolored and brittle like this from flue gases. These are 2 96% eff boilers. We put them in all the time but I never go back and service them. I just happen to go back to this place to do something else and saw it. I know there's been discussions on eliminated PVC for the flue but if the manufacturer says its ok then it's irrelevant. I started using schedule 80 a while ago I never thought schedule 40 was a good idea it's for drains not flue gases the way I look at it. All I'm asking is of anyone has seen leaks or failure yet and not from installer error. Thx


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## Gettinit

Is it over firing?


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## Gettinit

Is it the condensate running down the outside of the pipe?

If it were charred I would be concerned but it doesn't seem to be the problem in the pic. Not sure what you mean by brittle because during the winter any PVC left outside will shatter.


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## Plumbworker

Out in my neck of the woods i'm required to apply a uv resistant paint over the pvc to prevent it from damage getting brittle etc... Maybe the vent is running pretty hot... I dont understand why these tards put in condensing boilers when running high temp systems that exhaust is gotta be running at least 180..


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## deerslayer

Team BP said:


> You only gotta be a foot from any window that opens but that's beside the point. What I'm asking is has anyone seen PVC flue pipe become discolored and brittle like this from flue gases. These are 2 96% eff boilers. We put them in all the time but I never go back and service them. I just happen to go back to this place to do something else and saw it. I know there's been discussions on eliminated PVC for the flue but if the manufacturer says its ok then it's irrelevant. I started using schedule 80 a while ago I never thought schedule 40 was a good idea it's for drains not flue gases the way I look at it. All I'm asking is of anyone has seen leaks or failure yet and not from installer error. Thx


A foot?? Maybe boilers are different but powervent water heaters differ a little between manufacturers but it's usually 6' or more from a window that opens.


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## Tim`s Plumbing

Team BP said:


> You only gotta be a foot from any window that opens but that's beside the point. What I'm asking is has anyone seen PVC flue pipe become discolored and brittle like this from flue gases. These are 2 96% eff boilers. We put them in all the time but I never go back and service them. I just happen to go back to this place to do something else and saw it. I know there's been discussions on eliminated PVC for the flue but if the manufacturer says its ok then it's irrelevant. I started using schedule 80 a while ago I never thought schedule 40 was a good idea it's for drains not flue gases the way I look at it. All I'm asking is of anyone has seen leaks or failure yet and not from installer error. Thx


 Navien has put warnings on their combi units that if you run the unit at temps above 140F the venting must be sch 80 cpvc.


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## moonapprentice

I would change them out... I have seen a pipe that was dark brown and the fittings melted to an abnormal looking state... I am sure those will keep getting darker and will create a fire hazard.


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## Plumber patt

3 feet to any open Window here


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## Catlin987987

1 Foot under 100MBH
3 Feet over 100MBH 
in Alberta(and I think all of Canada)


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## victoryplbaz

Your kidding about the discoloring....Really you dont know?? All pvc pipe that is expose to the direct sun light does that..even sch 80. and the sun isnt any different here in Az than anywhere else.


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## plbgbiz

victoryplbaz said:


> Your kidding about the discoloring....Really you dont know?? All pvc pipe that is expose to the direct sun light does that..even sch 80. and the sun isnt any different here in Az than anywhere else.


Why are the two middle pipes still white?


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## victoryplbaz

plbgbiz said:


> Why are the two middle pipes still white?


dont know..but i have had pipe do the same thing..some turned brown and some stayed white while sitting on a job. I guess the heat can speed up the process. Even pool piping thats pvc exposed to direct has some different shades of brown.

Dont use ABS pipe either..I tore some out that was few yeas old on a high effency commerical heater...broke like glass.


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## Gettinit

The best plastic in my opinion is CPVC for venting. The sun is going to effect any plastic unless painted.


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## JoshJ

What do the insides of the pipe look like? Shouldn't discoloration show up there if it's due to the boiler firing alone? What I'm seeing in the pic would make me check for an external source, once I had verified firing rates and flue temps. 

Up here I can only use pvc for water heaters and furnaces, boilers must be CPVC or PP.


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## Plumber patt

products of combustion are very corrosive and acidic, between that and direct sunlight on those pipes would definatley dis color them IMO


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## Gettinit

If the outside portion looks like that and the PVC at the boiler isn't black and melted I wouldn't give it too much thought. Write it up and take a pic. If you get the go ahead for a repipe great if not no big deal without the presence of CO in the boiler room. It has to be just from the sun. Why those two? Good question. I would have to ask the owners if they ran the combustion air out after the fact for some reason. If it were so hot to discolor the pipe that far away it would be melted at the boiler.


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## Greenguy

I have seen lots of PVC pipe that has the same brown colour, water lines under mobile homes they were frozen, someone has gotten heat too close to the pipe to thaw it out, it will cook it brown like that. Try it with a torch.


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## Gettinit

Greenguy said:


> I have seen lots of PVC pipe that has the same brown colour, water lines under mobile homes they were frozen, someone has gotten heat too close to the pipe to thaw it out, it will cook it brown like that. Try it with a torch.


 Yes, but I doubt someone is doing it to those pipes. :no:


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## Greenguy

No but the system may be running much too hot, I believe the S636 PVC back home was limited 65°, while CPVC was 85°.


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## Coolcanuck

We were just talking about this the other day, boiler flue's being to hot for pvc and the cost of the cvpc. Was a sales pitch on a polypropylene product that was just approved up here, sigh, new products...


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## rjbphd

Coolcanuck said:


> We were just talking about this the other day, boiler flue's being to hot for pvc and the cost of the cvpc. Was a sales pitch on a poly butylene product that was just approved up here, sigh, new products...


And who are you to say this without the proper FULL intro on this site???


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## theplumbinator

Is that solid core or cell core PVC in the pic? That may be your issue...


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## heeterman1

Team BP said:


> We put in these two boilers two years ago and it's pretty obvious which one is the exhaust. The inside looks the same. This is why I do all my flues in schedule 80 cpvc. I'm just wondering what you guys have experienced.


Check the flue temp.sch 40 will work as long has temp isn't over 140


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## Letterrip

rjbphd said:


> Are you a liencsed plumber??


Nothing to indicate that so far.


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## Catlin987987

rjbphd said:


> Are you a liencsed plumber??


Have you seen some of his ramblings?


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## rjbphd

Catlin987987 said:


> Have you seen some of his ramblings?


Yep, laughings about it


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## wyrickmech

It's probably a combo of things high temp in the exhaust it may not be over the 140 mark but could be close then you will have highly ascitic water and vapor from the boiler and sunlight. The intake only has the sunlight so the breakdown is slower and less noticed.


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## plbgbiz

rjbphd said:


> Are you a liencsed plumber??


He is no longer among us. :no:


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## MTDUNN

If it's brown in the building, that will rule out the sunlight and UV.


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## LIQUID

have you done a flue gas analysis ? I have not seen this but as others have suggested. 

1. sunlight ? 
2. acidic condensate 
3. high temp... this is where my money is.


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