Adjusting a sink pop-up is something that every homeowner should be able to do by following some simple instructions.
If the pop-up plug does not make a good seal in the closed position, begin your adjustment with the lift rod--the vertical shaft that runs down from the control knob and through the top of the lavatory.
Pull the knob up as far as you can, and free the rod by loosening the clevis screw with a pair of tape-wrapped pliers.
Press the pop-up plug down to seal the drain (the clevis rod will rise a bit) and re-tighten the clevis screw.
You may find that the pop-up mechanism is now slightly jammed and difficult to operate; if so, continue to the next step.
Next we will set the pivot rod.
With your fingers, squeeze the spring clip that holds the pivot rod in the clevis rod completely out of the clevis.
Reset the rod in the next higher clevis hole, threading it through the spring clip on both sides of the clevis.
Try the pop-up mechanism and, if necessary, repeat the step from the first paragraph.
There are generally several types of pop-up plugs, all of which do the same job, but methods of installing them and removing them vary widely.
If the pop-up plug is of the type that rest on the inside end of the pivot rod, then you must remove them by raising the plug to the open position and lifting it out of the drain.
Another type of pop-up plug engages the rod in a slot, and comes free of the rod with a quarter turn clockwise.
If you can't remove your pop-up by lifting or turning, then it must be of the type that engages the rod in a loop like the eye of a huge needle.
To disengage this plug, you must free the pivot rod and pull it partly or completely out of the drain T underneath the basin.