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  • Plastic Boiler/Furnace Vent Pipe

    As of the July 1 2007, there was an update to the GAs Code in my Province: Any Plastic Boiler Vent Pipe (PVC & CPVC) must meet a standard, called S.636 (I think it's CSA). So essentially when doing high efficiency boiler or furnace venting (or other high efficiency appliances) are must use these specific pipes for the exhaust vent (or we can also still use Stainless steel if we want). Obviously I'm talking about condensing appliances.

    When the standard was first unveiled, Ipex was the only manufacturer who had pipe that was certified to meet this standard and had a bit of a monopoly. The local wholesalers who carried this pipe seemed to carry a lot of PVC 636 but getting CPVC required special ordering for a while until one of our supply houses "wised up." But anyways, I remember pricing it out - the CPVC 636 in 3" was $9 per foot. Yes NINE DOLLARS PER FOOT!

    For plastic vent pipe? And that's the wholesaler discount cost for us too!

    Anyways - I find this new "standard" that we must follow interesting because for years everyone used solid core ABS or just straight Sch. 40 PVC for vent pipes for any high efficiency appliance. Are those plastic vent pipes now doomed to fail?

    Also - we are still allowed to utilize regular sch. 40 PVC for the condensate traps and they must be glued used a special transition glue to the PVC or CPVC 636 pipe. I find it interesting because there is the same acidic/corrossive condensate in these regular (admittedly not as high of a temperature) PVC Sch 40 condensate drains as in Boiler Venting itself.
    Also, apparently the main boiler manufacturer we install (IBC Boilers), they did some tests and found that the boiler temps, even on high temp loads which require CPVC at the immediate exit of the boiler - cool down quite quickly over the travel of the vent pipe to the point that you could effectively switch to PVC yet inspectors are still requiring the more expensive CPVC for the entire length for high temp loads. Keep in mind that PVC is rated for 65 Celsius (about 149 F) and CPVC is rated for 90 Celsius (about 203 F).

    So I'm curious - have any of you guys seen any major failures of plastic or even other types of vent pipes out there in your travels? What is your opinion of plastic venting on high efficiency appliances?

  • #2
    Re: Plastic Boiler/Furnace Vent Pipe

    I have not seen any failures yet, but the improtant thing to remember is that the manufacturers specifications always supercede the code requirement. So if the manufacturer says to use shc. 40 PVC, that's what you use. By the way, though most manufacturers don't say you can't use foam core, I would stay away from it.
    sigpic

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    • #3
      Re: Plastic Boiler/Furnace Vent Pipe

      I haven't seen any complete failures but we had to repipe 3 commercial water heaters in a hotel with stainless. The schedule 40 overheated and the PVC began to sag between the hangers collecting condensate.

      They were all installed to manufacturers specs.

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      • #4
        Re: Plastic Boiler/Furnace Vent Pipe

        On this topic:
        One of the referal companies employees(we'll just call him Ron for the hal'i'but)stopped by Rick's pipe pull.He had a story of a five year old 4" A.B.S. vertical vent with 45 degree offsets that had decomposed at the glue joints similar to where the damage was done on joints discussed earlier on non virgin ABS.He said when they had tried to pull it out of it's chase the thing fust fell apart.I have installed about 200 garage power vented heaters with ABS as per engineer/manu. on a condo project three years ago.I wonder how they are holding up.

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        • #5
          Re: Plastic Boiler/Furnace Vent Pipe

          Originally posted by NHMaster3015 View Post
          I have not seen any failures yet, but the improtant thing to remember is that the manufacturers specifications always supercede the code requirement. So if the manufacturer says to use shc. 40 PVC, that's what you use. By the way, though most manufacturers don't say you can't use foam core, I would stay away from it.
          Where I come from it's a bit different as you can see. Since the code now said you must use pipe that conforms to the 636 standard, they now must use PVC 636 and CPVC 636 for all plastic vent/exhaust pipes. In this case I don't see it as the code stepping on the manufacturers feet, but (apparently) ensuring these plastic vent pipes are up to snuff for whatever reason. But I always wonder where it suddenly comes from if ABS and PVC Sch. 40 have been used all these years with no apparent issues (or is there - why I'm surveying you guys).

          As far as ABS cell core versus solid, if I'm not mistaken Solid Core has a higher temperature rating does it not?

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          • #6
            Re: Plastic Boiler/Furnace Vent Pipe

            14 years and several hundred high efficient furnaces: I have had zero PVC failures on venting. My 2" is solid core and 3" is cell core.

            I did have a glue joint fail once. I learned my lesson on trying to clean/glue when its below freezing. After a year in service one joint started to drip condensation. I ripped the entire thing out and started over. Several years ago Arctic-Weld disappeared from this area. Since then I have been using clear Oatey cleaner (yellow label) and Medium bodied Oatey glue (medium green label). But now, I bring my diesel heater on new construction in the winter.

            Andy

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            • #7
              Re: Plastic Boiler/Furnace Vent Pipe

              Originally posted by Scott K View Post

              So I'm curious - have any of you guys seen any major failures of plastic or even other types of vent pipes out there in your travels? What is your opinion of plastic venting on high efficiency appliances?
              Originally posted by NHMaster3015 View Post
              I have not seen any failures yet, but the improtant thing to remember is that the manufacturers specifications always supercede the code requirement. So if the manufacturer says to use shc. 40 PVC, that's what you use. By the way, though most manufacturers don't say you can't use foam core, I would stay away from it.
              Originally posted by drtyhands View Post
              On this topic:
              One of the referal companies employees(we'll just call him Ron for the hal'i'but)stopped by Rick's pipe pull.He had a story of a five year old 4" A.B.S. vertical vent with 45 degree offsets that had decomposed at the glue joints similar to where the damage was done on joints discussed earlier on non virgin ABS.He said when they had tried to pull it out of it's chase the thing fust fell apart.I have installed about 200 garage power vented heaters with ABS as per engineer/manu. on a condo project three years ago.I wonder how they are holding up.
              Originally posted by Scott K View Post
              But I always wonder where it suddenly comes from if ABS and PVC Sch. 40 have been used all these years with no apparent issues (or is there - why I'm surveying you guys).

              As far as ABS cell core versus solid, if I'm not mistaken Solid Core has a higher temperature rating does it not?
              adam, you beat me to the point. i was going to ask the same question too

              this particular property was built from the ground up on property that everyone is well aware of
              fortunately our friend has noting to do with the original construction. he's involved with the service end of it.
              my feeling is the foam core abs is the issue. i would think that solid core pvc/cpvc/abs would have been the specs the manufacturer would have called for.

              i'll forward this thread to our friend for his review

              rick.
              phoebe it is

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