: AFTER REPLACING THE POP-UP AND WASTE UNDER MY BATHROOM : SINK, I CANT STOP A LEAK AT THE BOTTOM SIDE OF SINK : AND THE RUBBER WASHER, WHICH IS TIGHTEDED BY THE LARGE : NUT, MEET. THE WASTE IS METAL AND THE SINK IS CULTURED : MARBLE. THE REASON I REPLACED THE WASTE WAS BECAUSE : THE OLD ONE CRACKED ALL THE WHY AROUND, WHERE THE OVER : FLOW WHOLES WERE. IT DIDNT LEAK BEFORE IT CRACKED.: THANKS, STEVE Steve, Did you use plumbers putty under the flange in the sink?? If not, do so. Also smear a heavy coating of pipe dope around the rubber seal. Be sure to check for sharp or jagged edges arount the hole in the sink before installing pop-up. Good Luck.