Every year I inspect, service and reseal this HTPV flue. This year the elbow on the boiler flue exit split apart while I removed it. I tell you this for your edification, as I know plastic venting of all sorts is a hot topic here. Fortunately I was able to replace it with a SS Heat fab elbow I had on hand. Now I need to get the the rest of the plastic replaced with easy seal. Here are a few photos.