Two fixture holes on 4-, 6-, or 8-inch centers are common in bath sinks. The wider types are designed to accommodate a split-set faucet, which separates the faucet handles from the spout. A center set or a single-lever faucet can be installed in the 4- or 6-inch holes. Flexible supply tubes transport water from wall shutoff valves to threaded tailpieces at the faucet’s base.
A pop-up stopper is commonly installed in the drainpipe that goes through a bathroom sink, and it raises and lowers as you pull up or down on a knob or handle just behind the faucet body. The knob is actually the head of a lift rod that is connected to a clevis (a connecting bar). The clevis is attached to a pivot rod-and-ball assembly, which comprises a rod that goes through a rubber pivot ball and slopes uphill to the stopper’s tailpiece.
The pivot rod pushes the stopper up when the knob and lift rod are pushed down; the pivot rod pulls the stopper down when the knob and lift rod are pulled up. If you wish to get rid of the assembly, you might be able to just pull it out. To detach it from the clevis, you may have to twist it.
A flange on the sink drain is sealed to the sinkhole with the plumber’s putty. This flange is screwed into the drain body, which is held in place by a locknut on the underside of the sink basin.
Slip-joint couplings connect the tailpiece, which can be attached to a pop-up stopper, to a drain trap. To prevent sewage gasses from entering the room, a sink trap is filled with water and attached to a threaded nipple inserted in a T in the drain line. The connection is concealed by an escutcheon trim.
A set of levers and rods controls a mechanical pop-up stopper. If this isn’t working properly, the answer is generally as simple as adjusting the clevis screw or pivot rod location.