I'm in the grey tank,I remove the 3 inch connector at the tank)1 1/2inch pipe connects to this connector ,which is glued into the tank, The tank has a side mount drain and it does have a good slope to it. The tank is molded so there was no cut out,it was molded with the outlet in it. I thought it would be a cut out also,,but being molded one piece,thats not the case as I have found out. The tank had lots of soap scum on the walls of the tank,but nothing that would not plug the drain .I'm wondering now if it might be some type of vent problem. Keep them coming.Thank you