I told him to use a y fitting on the house side of the trap . H e eMailed me later and i told him that. H e sent me a pic. of the disp. con. with a center outlet waste and I told him that was wrong, I guese it is okay with you. I told him to run trap over to disp. and use end outlet waste to con. other bowl and us e a Y tailpiece on house side of that for the RO.