A shower drain consists of a grid, a strainer, a vent, a trap, a pan and a cap. The cap, grid and strainer allow water to pass to the drainage pipe while trapping hair and other debris. The pan is the inclined surface surrounding the drain that collects water and directs it toward the drain. The trap consists of a U-shaped pipe below the shower surface that prevents gases from being directed upward while the vent prevents water from escaping upward. You can often replace a shower drain in an acrylic or fibreglass shower without cutting holes in the ceiling below.
Insert a screwdriver into the existing screws and remove the drain cover. For threaded nut and gasket seal systems, grasp the compression gasket assembly using a needle nose pliers, prying loose the compression nut from the gasket and removing both from the drain. For drains with a three-part seal on the gasket, after removing the drain cover, insert drywall screws into the 3 rings on the gasket and remove the three rings and the gasket from the drain seal.
Cut two vertical slits, 1 inch apart, on the edge of the drain body with a hacksaw without cutting into the shower pan. Cut two horizontal slits on the drain flange (the horizontal ring surrounding the top of the drain) 1 inch apart.
Slide a flat screwdriver underneath the cut area of the flange and press the screwdriver upward and pry off the cut section of the flange. Pull up the existing shower drain to remove it from the drain pan and apply a thin coat of liquid soap to the inside of the O-ring (the area farthest from the flange) of the new drain.
Apply an even coating of silicone caulk to the underside of the flange of the new drain and around the inside of the drain hole. Insert the drain into the shower pan, hold into place and tighten the screws of the new drain using a screwdriver. Place the drain cover over the new drain and tighten the screws into place with a screwdriver.
According to WingTite, replacement drains are often based on a standard 2 inch diameter PVC or ABS drain, but adaptors for 1.5 inch copper 2 inch copper pipe DWV (drain waste vent) are available.
When selecting drains, you must select the type of drain appropriate to either PVC or ABS drainage systems, which refer to the type of plastic constituting the drainage system.