Currently I have a condensate pump servicing my furnace (4 ton heat pump, although Oil backup) as well as a GE GeoSpring Heat Pump water heater. I also burn 4-5 cords of wood a year to keep from having to use oil, which had me considering adding a whole house humidifier to the mix.

Currently the condensate is pumped outside using some 3/8 poly tubing, but now I am concerned about it freezing. Currently in winter, I have the GeoSpring's heat pump turned so it's not condensating. However, adding the humidifier would likely cause it to freeze. I'm located in Maryland which will see the single digits occasionally.

It is installed in a crawlspace, there are no floor drains or utility sinks. I know I cannot plumb in directly to the DWV. I am curious though if I could T into the drain (pre-trap) for the side of the kitchen sink. This is approximately 15 feet away, and roughly 6 feet higher than the pump.

I found this picture and was curious on your thoughts... (Fig on top/right)