I work for a home builder and we are trying to figure out a better way to make the drain connection at the washing machine overflow pan.
Right now, we have a 1" pipe coming up out of the floor with a threaded end (it's the standard fitting, similar to what you can buy at Home Depot). We drill a hole in the bottom of the plastic drain pan, slide it over the pipe, install a black rubber washer, and screw on a nut to secure it.
Additionally, we have been applying a bead of silicone before and after sliding the washers on, but it doesn't help. The main problem is that, whenever the drain pan is rotated (which invariably happens when the installer is trying to lift the washer up over the lip into the pan and slide it around), the silicone seal is broken.
The rubber washer, with or without silicone, never seems to keep things watertight. It's obviously rare that a washer leaks, but 9 times out of 10, the pan drain seal doesn't hold and the water ends up leaking down through the floor to the dining room below instead of making it into the pipe.
Does anyone know of a better solution??