How to Stop Downstairs Toilet From Bubbling When Upstairs Toilet is Flushed

Written by

Paulk Webb


Freddie J. Hagopian

Saveourwaterrebates is reader-supported. When you buy via our links, we may earn a commission at no cost to you. Learn more

how to stop downstairs toilet from bubbling when upstairs toilet is flushed

You may find it odd why one toilet bubbles when the other is flushed, especially when they are 1-floor level apart. But this should not be taken lightly as it indicates a serious problem within your home drain system.

Air bubbling out of the toilet means the normal airflow in your home’s drain system is disrupted, causing a build-up of suction or negative pressure in your drain pipes. This must be fixed immediately so air and waste can pass through normally.

This guide can help you identify quick fixes for the problem and what might be causing it, so you will know how to stop downstairs toilet from bubbling when upstairs toilet is flushed.

Steps to Stop the Downstairs Toilet from Bubbling When the Upstairs Toilet is Flushed

You can either try do-it-yourself fixes or call for professional help, depending on the severity and location of the blockage. Here are different ways you may stop toilet gurgling after flush:

DIY Solutions

If your guess is it’s a minor clog causing the disrupted airflow, then you can start with DIY remedies using tools you probably have at home. Consider trying these methods to clear the clog on your own:

Unclog Sing the Good, Old Plunger


Try to ‘push down’ that toilet obstruction using your trusty plunger first. The pressure created should be enough to dislodge light clogs in your drain pipes.

Before proceeding, seal off all drains from other bathroom fixtures (sink, bathtub, shower) to ensure the plunger’s force can be directed to the blockage and not just escape through other openings since all of them share the same drain line.

Fill the bowl with water and pump forcefully about 10 to 15 times. If your downstairs toilet gurgles still, then you may need to consider other methods.  

Clear It Out With a Plumber Snake


If the clog is much deeper down the drain, then plumber snakes, also known as toilet augers, will be more helpful in this case. This tool can either pull out or break that pesky clog.

Manual toilet augers are more common in the household setting. It will pick up or break apart debris as it travels and rotates inside the pipe. However, this type of snake can only reach about 5 to 15 feet.

On the other hand, motorized or mechanical snakes can reach up to more than 100 feet down the sewer; but you’ll need to remove the toilet bowl since it is too big to be inserted in the opening directly.

Check and Clean the Vent Stack


The first two methods deal with clogs in your toilet pipes, but this is not the only reason for a gurgling toilet. If neither was able to fix the problem, then you may want to check out the vent stack up in your roof.

Debris, like leaves, branches, and even small animals, are very likely to accumulate inside your vent pipe. With these obstructions at hand, your drain system’s ventilation will not work ideally – causing toilet gurgles at the end of flush.  

Professional Solutions


If none of these DIY suggestions seem to work, the problem may be severe, or it could be in your neighborhood’s sewage system already. Either way, it’s best to resort to professional help.

  • What you can do is to call different plumbing professionals and ask them to quote for the extent of the damage and the amount needed to fix it.

Compare their opinions with each other and choose the plumber you think offers the best deal.

  • But if you already have a trusted plumber, then it’s best to contact them so your mind can be at ease while they work their way through your drain system..

Your plumber may ask about some common symptoms like:

  • foul septic smells
  • leaks
  • low water pressure
  • or an overflowing toilet.

These are all indicative of severe problems in your toilet and its drain pipes and should be answered truthfully.

Meanwhile, an indication of problems occurring in your community’s sewage line is toilet gurgling when it rains heavily. You may also want to mention this to your plumber for better output.  

What Causes the Bubbling? Why does It Happen?


Clogs in the main sewer line or vent stack interfere with the normal airflow in your home’s drain system – creating negative air pressure or suction.

This ‘air clog’ manifests as the gurgling or bubbling we commonly see in a toilet when upstairs tub drains, or any other bathroom fixtures, are flushed.

In this illustration, the typical home drain system can be seen as interconnected; and both upstairs and downstairs toilet water moves into the main sewer line.

An upstairs tub draining into the downstairs toilet is common for a typical 2-storey drain system.

So, when the upstairs shower is used, or when the shower is running, in general, it’s not a surprise your basement toilet bubbles.  

As discussed, depending on its severity, you may opt to try and fix it yourself first or call for professional help. What’s important is to address this immediately since bigger problems arise when this ‘simple bubbling’ is overlooked and prolonged.

Preventative Measures


Taking good care of your drain line and vent stack to avoid clogging is the primary preventative measure needed.

Only human wastes are meant to be flushed down the toilet without causing problems. Avoid dumping bathroom items like Q-tips, hygiene products, diapers, wet wipes, and many more to prevent the occurrence of clogging.

As for the vent stack, regularly cleaning the pipes can save you lots of money compared to drain problems getting out of hand. Also, if there are trees around your roof area, consider trimming the branches to lessen the chance of accumulating debris.


Is a Gurgling Toilet Dangerous

A gurgling toilet becomes dangerous when the problem is ignored for prolonged periods of time. If not fixed immediately, sewer wastes and gas would flow back up, leading to very nasty and even hazardous conditions.

If your toilet flushes slowly, gurgles, leaks, and smells awful, this is already a strong indicator to find what’s wrong and fix the problem as soon as possible.

How Do I Know if My Vent Pipe is Blocked?

Some common signs of a blocked vent pipe are as follows: gurgling drains and toilets, foul sewage smell, and sluggish drains.

Vent pipes, sometimes referred to as vent stacks, are very susceptible to clogging. Since they are sticking out of your roof, things like leaves, branches, bird nests, and other debris are likely to accumulate and cause an obstruction inside it.

When the downstairs toilet backing up becomes a recurring problem, don’t wait any longer and have it fixed immediately.

How Often Should I Have My Plumbing System Checked?

It is recommended to have plumbing inspections once every two years. Invest in check-ups with your trusted plumbing professionals to address possible problems and damages that will incur much more expenses if left unchecked.

Common Toilet Plumbing Issues and Solutions

Listed below are some common toilet plumbing problems and how to fix them:

  • Toilet clogs – unclog with a plunger, toilet auger, baking soda + vinegar, or commercial cleaners.
  • Toilet leaks – tighten the flapper, replace the gasket, or tighten the valve screw.
  • Whistling tank during flush – replace the tank fill valve.
  • A toilet that flushes up sluggishly – similar to unclogging toilets, use a plunger, drain snakes, home or commercial chemicals.
  • Rocking toilet – tighten flange bolts or insert shims under the base.


It can be confusing at first when you flush the upstairs toilet, the downstairs bubbles. But given its intricateness, an issue in one pipe affects the entire drain system.

Since we want immediate action on this problem, we hope this guide on how to stop downstairs toilet from bubbling when upstairs toilet is flushed was able to help you get the important ideas in addressing the said toilet issue.

5/5 - (2 votes)