When I Flush the Toilet Water Comes up the Shower

when I flush my toilet, water backs up the drain in the shower

It is a frustrating experience: you flush the toilet, and instead of the water flowing quickly down the drain, it starts to come up your shower. Unfortunately, this problem is more than just an annoying inconvenience, as it could indicate a significant issue in your home’s plumbing system. 

Correcting the problem is not as difficult as learning to remove a shower head, but it does take patience.

Why is it when I flush the toilet, water comes up the shower? When you notice toilet water coming out of your shower drain when you flush, it is due to a blocked sewer line. Typically, a home’s plumbing system drains through a branch line that ties into a larger main sewer line. When this main sewer line is blocked, the water backs up into the branch lines.

I will explain the reasons why this blockage is happening.

Tree Roots 

As the roots grow and spread beneath the surface, they can crack and collapse the pipes or even create blockages that prevent sewage from properly flowing away from your home. 

Foreign Objects

Toilets are designed to handle human waste and toilet paper, and anything other than that can cause severe plumbing problems. When foreign objects such as paper towels, feminine hygiene products, or even toys are flushed down the toilet, they can get lodged in the pipes and create a blockage.

Article Recommendation: If you are experiencing a shower knob that won’t turn all the way, it is important to first identify the source of the problem. It may be a broken or stuck internal part, such as a valve stem, or it could be caused by a mineral buildup on the knob.

As a result, when water is flushed down the toilet, it cannot flow through the pipes and instead starts backing up into your home’s plumbing system, including your shower.


Hair is another common item that can cause plumbing problems when disposed of improperly. While it may seem like a small issue to let hair go down the drain, over time, it can accumulate and create blockages in pipes, leading to slow drainage or backups.

Pipe Scale

Pipe scale is a buildup of minerals and other sediment in pipes, which can cause blockages and restrict the flow of water. Over time, minerals in the water can accumulate, forming a hard coating on the inside of the pipes. 

This scale buildup can become thick enough to impede the flow of water and lead to backups into your shower drain.


Flushing grease down your drain may seem like a convenient solution, but it can lead to significant plumbing problems down the line. When grease is washed down the drain, it can solidify and stick to the inside of pipes, eventually creating a blockage that can cause slow drainage or backups, including water emerging from the shower drain.

Blocked Vent Pipe

A blocked vent pipe can cause backups into your shower or other plumbing fixtures after you flush the toilet. This occurs because the clog in the vent pipe prevents air from entering the drainage system to regulate the pressure.

How to stop Your Toilet from Backing Up into Your Shower

Experiencing a backup into your shower after flushing the toilet is not just frustrating, it’s also unsanitary. The good news is, there are several ways to stop this from happening. Here are some options:

Snake the Toilet Drain: Using a plumbing snake can help clear any blockages in your main sewer line that may be causing the backup. Feed the snake into the toilet and maneuver it down the drain until you hit the blockage. Turn the snake clockwise to break up the clog, then pull the snake back up through the toilet.

Article Recommendation: Learn how to dry yourself without the use of a towel after a shower. Explore techniques such as using a blow dryer, rubbing your skin with a microfiber cloth, or using a no-towel method.

Try Dish Soap and Hot Water: Pour a generous amount of dish soap down the drain, followed by a pot of boiling water. The soap will work to dissolve the blockage, while the hot water will help flush it through the pipes.

Use a Wire Coat Hanger: Straighten out a wire coat hanger and create a hook at one end. Feed the hook down the toilet drain and move it around to break up the blockage. Pull the hanger back up through the toilet and repeat, as necessary.

Baking Soda and Vinegar: Sprinkle a cup of baking soda down the toilet, then follow it up with a cup of vinegar. The chemical reaction will create a foaming action that can help dissolve the blockage. Wait a few minutes, then flush the toilet with hot water.

Use a Plunger: Try using a plunger to suck out the clog. Make sure to create a tight seal between the plunger and the toilet drain before thrusting up and down.

Aron Blake

I am the lead copywriter on Homezesty and the Webmaster. I have a lot of experience in home renovations and the creation of style. I enjoy writing and sharing my tips on how to create the best living environment. My Linkedin Profile, My Twitter Account

Recent Posts