Is the Dura-vent Pro replacing the standard Dura-Vent for pellet stoves or are they two separate lines? I saw on a web site that the 3" Dura-vent Pro Tee (3PVP-T) is a replacment for the 3067 Tee. If this is true can I mix Dura-vent and Dura-vent Pro in the same venting system?