# Plastic Boiler/Furnace Vent pipe



## Scott K (Oct 12, 2008)

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?


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