What Is a Kitchen Strainer Coupling?

Strainer Function

• A kitchen sink’s strainer, otherwise called a drain basket, provides a connection between the kitchen sink and the drainpipes underneath. The top of the strainer is recessed, allowing you to place a stopper inside to trap water inside the sink. The underside of the sink’s strainer is threaded, allowing you to tighten the strainer against the sink by threading a locknut onto the strainer. The bottom of the strainer has an opening that connects to the drainpipes, transporting the water that flows through the strainer into the drainpipes.

Coupling Location

• The coupling sits on the very bottom of the sink’s strainer, where the drainpipes initially connect to the strainer. The coupling, like the drainpipe sections’ coupling nuts, threads onto the drainpipe and makes a watertight connection between the strainer and the drainpipe. A loose coupling allows water to leak through the threads and into the sink’s cabinet. The coupling actually fits over the drainpipe’s lip, but it threads securely onto the strainer.

Coupling Installation and Removal

• When you install or remove the coupling on the bottom of the sink strainer, you may find that the whole strainer or basket spins if the plumber’s putty or silicone caulk is either not installed on the strainer or the seal has been broken. If this is the case, you must hold the strainer steady by inserting a wrench’s handles into the strainer’s grids. Wedge a screwdriver between the wrench’s handles and use the screwdriver to keep the wrench and the strainer stationary. Remove the coupling with slip-joint pliers.

Other Parts

• The sink strainer’s coupling must not be confused with the locknut or other parts that attach the strainer to the underside of the sink. Between the locknut and the sink sits a rubber gasket as well as a cardboard friction ring. The gasket helps keep a watertight seal on the bottom of the sink, while the cardboard friction ring absorbs shocks that would cause the locknut to loosen. The locknut sits almost against the sink and is larger than the coupling.