Our furnace is in an attic, above a two story home. The installed condensate drain runs to an outside wall and drips. The slightly corrosive condensate drips onto a piling with a steel connection holding one of the main glue-lams to a marine piling. The house is on a steep hillside. The piling started to split last year so I ran some extensions to the 3/4" PVC to redirect the drainage under the house, away from our pilings and into the ravine. I insulated the PVC but it's a fairly long run (20+ feet vertical plus another 20+ sloped downhill) and although it is steeply angled down the slope, it froze last winter twice.
The question is: Can I redirect the 3/4" drain into an air vent that runs through the attic? It's the washing machine drain from the laundry room below the attic and the vent rises through the attic to (and beyond) the roof.
2nd question: Do I need to add another trap to the vent line at the condensate entry point?