How to Install a Compression-Style Shower Drain
Compression-type shower drains attach to the home drain pipes with compression washers and nuts. This style is generally easier to install than solvent-glued drains, especially if you don’t have basement or crawlspace access to the area below the shower base. Compression-style drain assemblies are available in ABS, PVC, or brass, though PVC is gradually becoming the most popular. Any of these material types can be used with steel, fiberglass, or acrylic shower bases.
When installing a compression shower drain, the drain fitting is normally installed into the shower base before the base is laid into position.
Trim the Drainpipe
For a compression-style shower drain fitting, the drainpipe should come up to about 3/4 to 1 inch below the lip of the shower drain (follow manufacturer’s recommendations). You may have to test-fit the shower base to mark the right height, then remove the base to cut the pipe.
Trimming the drain pipe can be done with a hacksaw or plastic tubing cutter. If using a hacksaw, make sure to make the cut so it is flat and level.
Attach the Drain Assembly
Apply a bead of silicone caulk around the top flange of the shower drain opening, then insert the drain assembly into the opening. Put the rubber sealing washer and cardboard friction washer over the drain assembly tailpiece from under the shower base. Thread the mounting nut onto the tailpiece and tighten it down with channel-lock pliers.
Wipe away any excess caulk that has oozed out around the drain assembly.
Position the Shower Base
Carefully position the shower base so the drainpipe extends up into the drain assembly.
Insert the Compression Gasket
Place the soft rubber compression gasket down into the drain opening so it fits around the drainpipe. Thread the compression nut into the drain opening and tighten it. Compression-style drains usually come with a fitting tool that helps you tighten the nut from inside of the drain using a screwdriver. As you tighten, the rubber gasket is compressed against the drainpipe, creating a watertight seal.
Remove the fitting tool and snap the grate over the drain opening. Allow the silicone to cure for a full 24 hours before using the shower.
How to Install a Solvent-Glued Shower Drain
Solvent-glued drain assemblies are recommended only when you have access below the shower from an unfinished basement or crawlspace. If you don’t have this access, a compression-style drain assembly is a better choice.
Solvent-glued shower drain assemblies are usually PVC plastic, though older ones may use ABS plastic. If you have a plastic drainpipe, make sure to match the shower drain to the type of plastic in the drain system. Like compression-type shower drains, this type can be used with steel, fiberglass, and acrylic shower bases.
With solvent-glued fittings, it can be harder to get the pipe measurement right, so make sure to measure carefully and test-fit the pieces before gluing.
Adjust the Drainpipe
Follow the manufacturer’s recommendations for adjusting the drainpipe to the proper height. For many drain fittings, this means trimming off the pipe at the exact level of the subfloor.
Prepare the Drain Assembly
Most solvent-glued shower drain assemblies come in several parts: a strainer cover; an upper body that extends down through the drain opening in the shower base; and a lower piece with female threads that screw onto the upper body, with a smooth female socket that is glued onto the drain pipe.
Begin by disassembling all parts of the drain assembly. Carefully set aside the cardboard friction washer and the rubber sealing washer.
Insert the Upper Body of the Drain Assembly
Apply a bead of silicone caulk around the flange of the shower drain opening. Immediately set the upper body of the drain assembly into the drain opening and press down.
Secure the Drain Assembly
From below the shower base, place the rubber sealing gasket, then the paper friction gasket, over the male threads of the upper body. Then, thread the lower body of the drain assembly onto the upper body. Tighten the drain assembly by screwing the pieces together until silicone oozes out between around the flange of the drain opening.
Wipe away any excess silicone. Attach the metal grate to the top of the drain assembly.
Solvent Glue the Drainpipe to the Drain Assembly
From below the shower base, spread plastic pipe primer around the outside edge of the drainpipe and around the inner surface of the smooth socket on the lower drain body. Spread a thin layer of solvent glue on the same surfaces. Immediately slide the drain pipe into the socket on the drain body and hold it in place until the bond hardens. Let the solvent glue and silicone caulk cure for a full 24 hours before using the shower.
How to Install a Tile Shower Drain
Drain assemblies for custom-tiled showers are three-piece units, each of which is installed at different phases of the tile pan installation. The waterproof membrane liner for the shower is sandwiched between two lower flanges, which are bolted together. This liner is the lowest layer of water resistance and will make sure anything getting in under mortar will still go down into the drain and not leak through the shower pan. The final piece, the strainer assembly, is the only piece that is visible when the shower pan is completed.
If a tile professional is installing your custom shower base, they will handle the drain installation as part of the process.
Install the Bottom Flange
After the subfloor of the shower is prepared and clean, install the bottom flange of the shower drain into the drainpipe, usually by solvent gluing.
After this is done, a bed of mortar is troweled around the drain opening, creating a 1/4-inch-per-foot slope away from the walls and toward the drain. When the mortar bed has dried, a waterproof membrane liner is installed over the floor and the lower flange of the shower drain. Use silicone caulk to seal the liner to the drain flange, then trim away the liner around the drain opening.
Install the Middle Flange
Insert the middle flange of the drain fitting over the liner and drain opening, using bolts to secure it to the bottom flange beneath the liner. The liner will be tightly sandwiched between the flanges. At this point, it’s common practice to pour water over the shower pan to check the liner for leaks.
Install the Strainer Assembly
Attach the drain strainer assembly to the drain, so it extends up above the liner. This piece usually has male threads that screw down into the female threads of the middle flange. The degree of extension for the strainer assembly depends on how the tile will be installed—follow the manufacturer’s instructions. It may be as much as 1 1/2 inches if you are laying tile on a solid mortar bed.
Now you are ready for the rest of the ceramic tile installation. Usually, this involves a second layer of mortar, then ceramic tile applied over the mortar. The tile should be grouted, sealed, and cured before you use the shower.
Source: The Spruce