Use our shower drain plumbing diagram to understand how your shower works
Shower drains are complex plumbing systems that are essential for safely transporting wastewater out of your home.
Homeowners should know five key components: the strainer, the riser, the P-trap, the vent stack, and the drainpipe.
Common shower drain issues include clogged P-traps and dried P-traps.
Major issues with P-traps, vent stacks, and drain pipes should be left to licensed plumbers.
Shower drains are an important part of our total home plumbing system that we take for granted. We turn the water on, enjoy the soothing hot water after a long day of work, and expect the water to simply wash away to the main drain line and out into the sewer—without any sewer gases filtering into our home.
Several essential shower drain components make this happen. Below, we’ll look at a shower drain plumbing diagram to understand how these various parts work together and discuss what to do if your drain isn’t working properly.
Your shower drain is a complex network of pipes with various components, but we can really boil it down to five core parts that the average homeowner should know about.
The strainer is the only part of the shower drain that you should be able to see in your daily life. It’s the cover over the top of the hole in the shower floor that leads into the actual drainage system, and it’s designed as a barrier to keep soap scum, hair, sock fuzz, and other debris from entering the drain.
You may also hear this part referred to as a drain cover. While your drain can technically function without a strainer, you’ll have to deal with a lot more debris getting into your drainage system—and, thus, more frequent clogs.
The riser is the vertical pipe directly beneath the strainer. Water that drains from the shower goes down this pipe and through the P-trap (see next section) before filtering out through the main drain line that carries wastewater out of your home.
The P-trap is an essential component in your shower’s drain system. Without it, sewer gases would filter in from the main sewer line, meaning noxious fumes from everybody’s waste would enter your home. That’s why every plumbing fixture, from toilets to showers to sinks, includes some kind of trap.
How do P-traps work? Water sits in the bend of this U-shaped pipe, creating a seal that prevents gasses from passing through. (The pipe also looks like a P that has been turned on its side.)
When you run the shower and water filters down the riser, it pushes the water sitting in the trap outward toward the drain line. However, when you shut the water off in the shower, a new collection of water gets “trapped” in the P-trap, maintaining a barrier to prevent gases from flowing through.
Because of this shape, P-traps can commonly become clogged. There are several ways to unclog a tub drain, including using a trusty plunger or, for a more effective solution, by unclogging the shower drain with a drain snake or auger.
While over-the-counter cleaners are rough on your pipes, we do have a few homemade drain cleaners that are safe to use, which we recommend in a pinch.
Want to get rid of a clog in your shower’s P drain? Read our guide on how to unclog a bathtub in six easy steps.
Similarly, your P-trap can dry out; that is, there are scenarios in which water won’t get trapped inside the bend, and noxious sewer gases can enter your home. It’s important to run water down the drain regularly to prevent this. If you have a guest shower that doesn’t get used often, for instance, it’s still important to run the water once a week or every few weeks for a few seconds just to refresh the P-trap.
P-traps can also dry out faster in dry climates or during the winter when the heater is run more often. They may also dry out if there are issues with the vent stack.
Any plumbing fixture with a trap, including a shower, needs a plumbing vent. A vertical pipe connected to the horizontal drainage pipe will travel upward toward the roof of your home to vent.
Air moves down this vent stack as waste moves through the drain line. This allows the water to move more smoothly through the plumbing system as it drains. Without this assist from the vent, the water may flow more slowly (or even result in standing water in your tub). If there are issues with the vent stack, you may also hear gurgling sounds when the water drains and fumes from the sewer may pass through your drain (if the P vent is dried out).
The drain line is the ultimate destination for your wastewater. After it successfully descends the riser and passes through the P-trap, water will travel to your home’s main drain line and out to the sewer.
Maintaining your shower drain is easy, especially if you regularly use the shower. Routinely allowing hot water to flow down the drain should replenish the water in the P-trap, and using a drain cover over the strainer can prevent hair and other debris from getting caught in the trap.
If you don’t use the shower regularly, pour hot water down the drain once a week or every few weeks. You can also pour vinegar and baking soda down the drain as well to unclog the shower and remove foul odors.
Unclogging a shower drain is an easy enough DIY project. You’ll just need to spend $20 to $40 on a drain snake or auger—or even less if you make a homemade cleaning solution. Sometimes, a simple plunger is enough to unclog a drain (though we recommend having a separate plunger from the toilet plunger).
If there are larger issues, like with your home’s main drainpipe, the vent stack, or a leaky trap, we highly recommend calling a shower installer near you to assess the problem and make the changes. How much it will cost depends on the source and severity of the problem. On average, plumbers cost between $45 and $200 per hour. There’s usually a service fee just for showing up to assess the problem.
