A sink drains by way of several components. The strainer fits into a strainer body that's inserted down through the sink hole and sealed with a bead of plumber's putty.
Underneath are a rubber gasket and metal washer and a large locknut or retainer tightens the body in place. A straight tailpiece mounts to the strainer body with a threaded coupling.
Slip joint couplings connect the tailpiece, the main parts of the trap and a short threaded nipple at a tee in the drainpipe. At the wall or the back of the cabinet, a trim piece called an escutcheon hides the connector and the nipple. The sink trap, always filled with water, seals the pipe so sewer gasses won't enter the house.Waste water exits through the trap, down the vented drain pipe to the main stack.
A garbage disposal, if there is one, mounts directly to a special strainer body. The trap then connects to an outlet on the disposer. Kitchen sinks may have single or multiple bowls in a variety of shapes and sizes. They're mounted in three different ways, depending upon the type: self rimming, flush or under-mounted. Self rimming sinks have a molded edge that overhangs the countertop. Flush sinks are supported by metal strips around the perimeter or are an integral part of the countertop material. Rimless or under-mount sinks are fastened or fused to the underside of the countertop.
