Step 7 · Apply Plumber's Putty or Sealant
If the leak is coming from the drain flange where it meets the sink, or if you've disassembled and reassembled a joint that still weeps, apply a ring of plumber's putty around the underside of the flange before inserting it into the drain hole, or apply a bead of silicone sealant around the joint after reassembly. Clean excess putty or sealant that squeezes out.