Most bathroom sink drains come in three pieces(besides the pop-up assembly). They are the top head piece with a flange, the pop-up assembly body, and the tail piece. Before installing the sink drain make sure the surface area that contacts the sink drain is clean and the old putty completly removed. Things you will need for installing a sink drain are plumbers putty, thread tape, plumbing pipe dope, a sink drain wrench, and a pair of channel-lock pliers. To easily install or remove a sink drain, a sink drain wrench is used to hold the sink drain body from spinning while you tighten or untighten the drain locknut. After you insert the drain into the sink the cardboard washer should be installed between the rubber gasket and the locknut.
After installing the bathroom sink drain and reinstalling the trap, check for leaks around the sink drain by plugging the sink drain and fill the sink with water. Check under the sink around the bottom of the drain for leaks, the common cause for leaks around the drain is the lock nut needs tightened. Some leaks are so small that it might take a few hours or a few days depending on the leak and how often the sink is used before the leak appears, for this i usully take a paper towel and leave under the drain. The next day if the paper towel shows drip spots there is a small leak which usully is not hard to find.
