The tub drain shoe is an elbow that channels water down the drain pipe, it is the first fitting attached to the bottom of the tub's drain basket. In order to remove and replace the shoe you need to access beneath the bathtub. Are all bathtub drain threads the same? One of the most confusing and annoying plumbing problems is replacing the bathtub drain (called a plug) that screws into the base (called a shoe).
