Toilet Backing Up Into Shower

Toilet Backing Up Into Shower: Common Issues and Fixes

If you’re reading this, you probably have a toilet that backs up into your shower but can’t pinpoint the exact cause. Toilet backup is hard to miss with its foul stench, gurgling sounds, and slow drains – all of which constantly remind you that your toilet, sinks, drains, and shower is part of an interconnected plumbing system. Your toilet may back up when something blocks or tears apart the plumbing.

The main cause of toilets backing up into the shower is blocked waste drain pipes. When the main sewer line is clogged, the waste is forced to exit through your shower drain. You can fix this by plunging or snaking your toilet and shower. If the problem persists, seek professional assistance.

In this article, we’ll analyze the most common causes of a toilet backing up into the shower and how to fix it.

1. Clogged Sewer Line

To understand the cause of a clogged sewer line, we need to go back to the anatomy of your home’s drainage (the series of pipes connecting your fixtures to the main sewer line).

Here are the most crucial drainage components, starting from the fixture drain to the main sewer line:

  • The fixture drain: This refers to the sink and shower drain that’s visible to us. Hair, soap, and solid particles often block fixture drains but can easily be removed with regular cleaning.
  • P-traps and u-traps: The fixture drain leads straight into a p-trap or u-trap. These traps are curved pipes containing water to prevent foul sewer gasses from penetrating your living space.
  • Branch drain lines: As the name implies, these pipes run from fixtures to soil stacks. These lines are often obscured behind your walls.
  • The main sewer line: The main sewer line carries solid and liquid waste from your home to the municipal sewer line. Depending on local plumbing codes, this pipe can measure 4 inches (10.16 cm) in diameter. The main sewer line is usually installed below your lowest floor.

Drainage is a vital part of your home’s plumbing. Problems arise when these pipes get blocked. A clogged sewer line could wreak havoc on your plumbing and cause water damage and potential health hazards. Potential causes of blockage include:

  • Gradual waste build-up (fat, grease, and debris being common culprits).
  • Tree roots.
  • Broken and misaligned pipes.
  • Wrong items flushed down the toilet, for instance, diapers and sanitary towels.

When main sewer lines get clogged, all the wastewater and its contents have nowhere else to go. As a result, it forces itself through your household drains, including your shower. Thankfully, there are several ways to unclog a clogged sewer line.

How To Fix

First, observing proper waste disposal practices is essential. For instance, it is never a great idea to pour excess grease and oils down the drain since they could solidify and cause serious clogging. Secondly, diapers, sanitary pads, and other solid waste should be disposed of using appropriate solid waste disposal practices.

  1. Active response to a toilet backing up into the shower begins with turning off the water to the house to ensure that there’s no more wastewater going into the drain pipes. 
  2. Seal the shower drain and use a plunger to dislodge the drain pipes’ solid matter. This can be done by inserting a bell-shaped plunger into the toilet bowl and flushing the toilet as you plunge.
  3. If the plunger doesn’t work, you may have to uninstall the toilet and snake drain. This can be done with a toilet auger, essentially a 3-6 ft (91.44-182.88 cm) cable. The cable can be pushed all the way down the toilet until it finds and pulls or dislodges the blockage from the pipe’s surface so that it flows easily with the current.
  4. Call in an expert for assistance if nothing else seems to work.

A clogged sewer line is a job best left to professionals. Expert plumbers have more hands-on experience with tools and technologies to unclog your toilet faster and more efficiently.

2. Clogged Drain Stack

A drain stack is a vertical pipe whose main purpose is to carry waste from different rooms and floors to the main sewer. To put things into perspective, branch drains connect to the drain stack, which then connects to the main sewer line. Drain stacks are also vented to allow sewer gasses to escape from the top of the building and balance out the pressure in the plumbing.

A clogged drain stack breeds a host of problems. As wastewater collects in a clogged stack pipe, your home gets filled with a foul smell since the waste has nowhere else to go. Slow drains and gurgling sounds are solid signs that your drain stack is clogged.

That said, what blocks drain stacks?

  • Wet wipes: Most people believe wet wipes are flushable because manufacturers and advertisers market them as flushable. Wet wipes should not be flushed down the toilet since they easily create a partial or full blockade for other waste traveling through the pipe.
  • Grease: Over time, grease poured down the drain solidifies along the pipe, eventually leading to blockage.
  • Other times, a defective or badly installed pipe could cause the blockage. This happens when a displaced joint provides a surface for objects to gather and block the pipe.

How To Fix

Unclogging drain stack pipes is a job best left to the professionals. Certified plumbers will perform a thorough inspection, locate the clog, and repair any damaged pipes at a cost. However, if you want to save money and have a little background experience in DIY plumbing projects, you can unclog your drain stack pipes in the following steps:

  1. Inspect your plumbing stack for any obstructions. Uninstall the toilet and inspect the p-traps for any clogs.
  2. Locate the drain clean-out, which could be inside your home’s basement or outside. In most cases, the drain clean-out is hidden from view.
  3. Use a drain snake to try to dislodge the blockage. Accessing the drain stack from the clean-out makes it easier to reach the clog faster and more efficiently without the need for a long drain snake.

While at it, you may also want to inspect the stack vent and clear any blockages. This can be done by going up the roof and running a plumber’s snake down the pipe. Take out as much dirt and debris as you can. You can also put a water pipe into the stack vent and let the water run at full pressure. If a frozen pipe is the cause of the blockage, pour hot water down the stack vent.

3. An Overfilling Full Septic Tank

The septic tank could be your next culprit if you do not have access to the main sewer line (as many people find it in rural areas). A septic tank gets rid of wastewater with no monthly fees, unlike the city’s drainage lines. Unfortunately, it can also be more challenging to maintain, especially if it’s heavily used.

Basically, septic tanks are buried under the front, side, or backyard. They filter wastewater through natural mechanisms, retain solid matter, and allow for partial decomposition of as much solid as possible. The wastewater is released into the surrounding soil while the solid waste can be pumped out.

Common signs of an overfilled septic tank include:

  • Sewage backing up into the household drains, including your shower.
  • Slow drains accompanied by gurgling sounds.
  • Unexplained, stinky pools in your yard near the septic tank.
  • Rapid grass overgrowth near the septic.

How To Fix 

When you notice any of these signs, it’s time to call a professional plumber. In the meantime, there are additional ways to intervene before the issue does more damage:

  • Start by turning off the water in your house. This way, no one flushes the toilet or uses the sinks to drain more wastewater into the septic tank.
  • Assess the area surrounding your septic tank. If you spot any still water, it could clearly indicate that your septic tank is overfilled.
  • Reduce the amount of water going into the drains. Excessive flushing drains more water into your septic tank, which, in turn, makes it difficult for solid waste to dissolve. As a result, the solid waste is pushed into the leach field distribution pipe, where it causes a blockage.
  • Only flush toilet paper and body waste down your toilet. Feminine sanitary products, condoms, and other solid objects should not be flushed since they could block the pipes.
  • Divert excess rainfall water away from your septic tank. When too much rain falls near your tank, the leach field’s perforated pipes will have trouble draining the wastewater into the soil. An easy solution would be to reduce the amount of water being used during heavy rains or planting flowers and shallow-rooted shrubs near the septic tank to help with drainage.
  • Cut down large trees and deep-rooted shrubs near the septic tank. Trees can do irreparable damage to your leach field and septic tank since their roots naturally grow toward water and nutrients.

Septic tanks demand care and maintenance. As such, they need to be inspected by a professional plumber once every three years. What’s more, you need to pump your septic tank at least once every three years, depending on its size.

Additional Ways To Prevent Sewage Backing Up Into Shower

The fixes highlighted above should suffice when it comes to preventing wastewater from backing up into your shower or bathtub. If nothing seems to be working up to this moment, there are several things you could do to prevent the problem:

Use Liquid Drain Cleaner To Clean Your Shower Drain or Bathtub

Liquid drain cleaners work by oxidizing solid matter. The reaction also causes the release of gasses that help unclog your pipes. Liquid drain cleaners contain several chemicals, such as sodium hydroxide, peroxides, and bleach. Generally, these cleaners are heavier than water and can help clear out many obstructions, ranging from food particles, lumps of hair, grease, scum, and soap. 

Unfortunately, not all liquid drain cleaners are safe to use. Some may corrode your pipes, leading to premature wear and tear. Liquid drain cleaners such as the Liquid-Plumr Pro-Strength Clog Destroyer (available on are safe for almost all drains and pipes. This cleaner can remove grease, hair, and soap scum removal in plastic and metal pipes. 

Before you proceed with this step, it is important to point out that liquid drain cleaners may cause an exothermic reaction that damages your drainage pipes with prolonged use. For this reason, they should be used sparingly. Beware of pouring these chemicals down your toilet bowl since they can damage your wax ring, leading to leaking.

Flush Down Chemical Drain Cleaning To Remove Stubborn Tree Roots

As mentioned earlier, tree roots are a menace to plumbing. Not only do they puncture through pipes and cause irreparable damage to your wastewater drainage lines, but they also catch other solid matter and prevent a smooth flow of waste material to the main sewer. The good news is that you can eliminate unwanted root growth in your pipes with chemical drain cleaning.

Chemical root killers such as Sanco Industries Root Destroyer (available on can easily get the job done. This drain cleaning product contains pure copper sulfate crystals that kill unwanted growth in your pipe along with some bacteria. Generally, it is recommended that you use chemical drain cleaners once or twice a year, especially when your leach line is located near a shrub or tree.

Still, it may take a couple of weeks before the dead tree roots are ejected from your waste drain lines.

Switch to a High-Pressure Toilet

Water is precious – and if you want to conserve nature, you’ll probably use a low-flush toilet to save as much water as possible. Low-flush toilets lower your bills by reducing the amount of water pushed down your toilet with each flush. Although these toilets save money on water, they often have little pressure to push down the waste all the way to the sewer line. This is a common issue we see in older toilets.

Newer low-flush toilets can easily overcome this issue, but to be on the safe side, you’re better off with an average household toilet that uses less than two gallons (7.6 L) per flush. Pressure-assist toilets are an even better alternative since they use pressurized air to push waste down the sewer and conserve water at the same time.

Switching to new toilets may demand a few changes to the existing drainage system (e.g., cistern and drain pipe modifications), which may come at an additional cost.

Consider Double Flushing

Your toilet can only flush down a fixed amount of waste at any given time. Flushing your toilet twice occasionally can help eliminate solid waste more efficiently. For instance, you may flush the waste the first time and then flush the toilet paper. Or simply flush the toilet twice.

Remember, constantly flushing more than once can waste an extra 1.6 gallons (6 L) to 7 gallons (26.5 L) based on the toilet’s design and size. Flushing twice should also be done when the water flowing into your toilet bowl is not enough. Other times, it’s a problem with the flapper. However, if your toilet can hold enough water in its tank, it would be advisable to flush twice occasionally.

Clean Your Toilet and Shower Regularly

Periodic cleaning, and maintenance ensure that your fixtures are functioning in optimal condition. We recommend cleaning your toilet at least once a week. Your shower should also be cleaned at least once a fortnight. 

Cleaning ensures that wastewater travels smoothly down the drain. Additionally, it reveals any issues in your drainage, such as potential leaks and cracks leading into the drain lines. That said, here’s how to clean your toilet and shower like a pro:

Cleaning Your Toilet

  1. Apply detergent, disinfectant, and soap to your toilet bowl and scrub thoroughly with a brush. This clears any waste that’s stuck in your toilet bowl. After scrubbing, rinse with clean water.
  2. Next, pour hot, boiling water down the toilet to eliminate any grease stuck inside the pipes.
  3. Prepare a vinegar and baking soda solution by mixing a cup (230 g) of baking soda into a cup (237 ml) of vinegar. This solution is safe for your pipes. Essentially, the baking soda and vinegar solution creates a reaction that releases carbon dioxide that helps dislodge dirt particles from your drainage pipes.
  4. Pour another pot of boiling water down the drain.

Cleaning Your Shower

Cleaning your shower with a hot water and vinegar solution should help get rid of dirt, scum, salts, and body oils stuck along the length of the pipes. You can also use liquid soap to clean your shower drain – simply pour it down the drain and scrub the fixture with a soft brush. 


A plumbing system in perfect condition keeps the wastewater collected from all rooms flowing smoothly. Any clogging that throws your home into mayhem should be fixed as soon as possible to prevent additional issues, such as potential health hazards, from backing up waste. If you’re unsure where to get started when the toilet backs up into your shower, get in touch with a professional plumber.

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