How to Plumb a Shower Drain

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Shower Drain

If you are planning to install a shower in your home, you will need to plumb the shower drain before the walls go up. This can be a challenging and time-consuming process, but it is a crucial step in the final outcome of your new shower and an important plumbing job to be done.

Drain Pipe Plumbing

When you remodel a shower, you must carefully consider how to plumb a drain pipe to avoid flooding. This can be tricky because you can’t see how a shower drain pipes will travel through walls and floors, but it’s important to get it right.

For a DIY job, the most user-friendly drain pipes are PVC and ABS. They’re relatively easy to cut and dry-fit, and you can connect them with a few tools.

Before fitting a shower drain piping to the P-trap, spread plastic pipe primer around the outside edge and inside smooth socket on the lower drain body. Apply a thin layer of solvent glue to the same surfaces.

Place the 2-inch shower drain waste piping, the male end of the street 90 elbow and the inside hubs of the U-bend onto the P-trap; rotate the pieces until the street 90 lines up with the 2-inch drain waste piping.

Tighten the P-trap with a screwdriver to seal the connection, then snap the strainer into place. A soft rubber compression gasket is usually included in the drain assembly, which helps to create a watertight seal between the drain body and the drainpipe.

Drain Trap

Drain traps, also called P-traps, are typically found in plumbed fixtures like toilets, sinks and showers. They provide a seal in the pipe that prevents foul-smelling sewer gasses from escaping.

Most modern homes have a trap beneath each toilet, sink and shower. They’re essential in preventing the passage of sewer gases into the home and providing an outlet for items that are accidentally dropped down the drain (like wedding rings).

The bend and arm in a drain trap are usually sold together as a kit, but you can buy parts separately. Depending on the configuration, you might need a tailpiece extension or other adapters to fit your plumbing system.

Start by unscrewing the slip nut washer and nut from the end of the tailpiece-the straight vertical pipe that connects to the bottom of your sink. Then slide the trap arm in to the drain opening at the wall. Tighten the trap arm and slip nut as needed. You should be able to get them all tight enough by hand, but you might need channel-type pliers to do a good job.

Drain Body

Most clogged shower drains are caused by snags of hair. The best way to avoid this is to use a plastic or rubber drain cover.

Then, to avoid the same snags and clogs down the line, make sure you always remove excess waste before rinsing off. This helps keep scum from building up inside your pipes, which makes the problem even worse.

Next, install a new drain flange (also called a drain basket) that connects the tub and drain to the drain pipe below it. To do this, apply a bead of plumber’s putty over the underside of the drain flange.

Test-fit the drain flange to the shower base and ensure it fits flush. If there’s any extra slack, you may need to cut the flange down.

Then, insert the compression gasket into the drain body and push it down until it sets against the bottom of the drain flange. Finally, tighten the compression nut. The gasket creates a watertight seal between the drain flange and the waste pipe.

Shower Pan Liner

Before installing a shower liner, it’s essential to plumb the base of the shower floor and drain. Then, the shower liner can fit over the base and into the drain without interference with its weep holes.

Most modern shower floors incorporate a flexible liner, such as PVC or CPE, beneath the tile and mortar. These membranes are a great replacement for outdated lead pans and are impervious to water and chemicals.

After a pre-sloped mortar bed is poured into the base of the shower floor, use a level to make sure that the sloped mortar bed is even from corner to corner. Then, apply a generous layer of water-impervious drywall to the wall studs to about 1’’ above the pan liner surface.

Next, screw the clamping ring bolts into the drain base to about 2-3 thread depth. Once the ring bolts are secure, slide the pre-measured pan liner over them and up the shower walls. Cut X shapes over the heads of the four bolts, so that the liner slides over them and down to the drain base.

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Casey Loeber

Casey Loeber is the founder of His mission is to share the best information online about plumbing jobs and help plumbers lead fulfilling careers.

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