Thread: Mixed vent materials

2 year old 90+ forced air furance... mostly PVC but has a couple ABS elbows. I could swear I read that's a no go but I can't find it in the manual or searching online.

Anyone have an opinion?

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The State of Idaho has said that two different venting materials like you discribed are not allowed.

Look up both pipe mfrs and see what they say about mixing their brand/ model pipe with other brands of similar material, much less other types of materials. I'm not aware of anyone advocating mixing types of plastic pipe. The plumbing code would probably allow it for DWV and in that application I would expect a Fernco fitting to be an acceptable transition.

However, with combustion appliances, esp. CAT IV, the code always point you to the appliance mfrs listed instructions.