My furnace has a bypass humidifier and another pipe that drain to a little pump. This little pump activates periodically, pushing the water up to a drain pipe (which ends up going straight back down to the floor, then onto the normal drain lines).
Is there any reason I can't just change these two pipes to go directly to the drain line, removing the pump altogether? Obviously they need to slope downhill, but there's plenty of room for it.
Secondary question: if I do this, do I need a trap?
The red arrows point to the drain lines going down to the little pump. The blue arrow points to the line going from the pump the drain lines. You can just see where it is loosely held via insertion into the drain line by the top right of the water softener.
Best Answer
See that tee fitting at the lower red arrow? That's the condensate output from the furnace. Burning gas in the winter produces liquid condensate in the furnace exhaust pipe; the condensate drains back into the furnace and out through this point.
The burner condensate drain is the lowest of the three water sources shown here. If you can re-arrange the drain stack so that there's a trap below this elevation, then yes you can eliminate the pump and let the furnace, air conditioner, and humidifier all gravity-drain into it.
Allow several inches of height (at least!) from the water level in the trap to the top of the stand pipe where the three drains converge. The reason for this is that you wouldn't want any overflow. More height above the trap supports building a little more pressure, which supports pushing a little more flow through the trap.