We have something similar. For a drain tube, I drilled a 1/8 hole in the reservoir at the bottom of the unit and slip fit a piece of tubing into the hole. I said it where the end of the tube drips in the drain and they had because there's no shut off on that drain even if all of my through holes are turned off. If ever I want to use it without it dripping all over the place I just have to pull the end of the tubing up higher so that it doesn't empty the reservoir.