Curious about why your toilet bubbles when you’re showering? Let’s unravel this plumbing mystery that can signal a broader problem.
Licensed plumbers Alexander Siv and Jason Duda explain what causes this oddity and offer practical advice for diagnosing and resolving the issue.
Why Does My Toilet Bubble When I Take a Shower?
According to Duda, there are most likely problems with the drainage system connected to the plumbing venting system. Siv agrees. “There’s some form of restriction in the venting,” he says.
Here are some possible causes for the bubbling:
Clogged vent pipe
Most plumbing systems share a vent pipe through the roof, ensuring proper air pressure and allowing sewer gases to escape. If there’s a blockage or restriction in that pipe from debris, leaves or even a bird’s nest, it can hinder proper flow of air.
When you run water down a shower drain with a blocked vent pipe, it creates negative pressure in the drain. As the drainage system tries to equalize the pressure, it can cause bubbling in a toilet as the pressure is released into the open water surface.
Clogged drain pipe
Tub/shower drain pipes can clog with hair, non-biodegradable products flushed down the toilet, residue buildup or a small toy. Any blockage in the drain connecting the shower and toilet can lead to a bubbling toilet.
“If the water flow is impeded, air bubbles can form and escape through the toilet trapway, leading to bubbling,” Siv says.
A clog can also cause water to back up into the vent pipe, trapping air in the drain line or impeding air flow. This can cause bubbling in the toilet as the drain line tries to expel or take in air in the toilet bowl.
Blocked sewer line
A clog in the main sewer line can trap air, causing toilet bubbles or gurgling. Sewer line problem are often caused by tree roots, damaged pipes or debris buildup. Signs include a sewer smell, more than one toilet bubbling at once, or one bubbling when another one is flushed.
Duda says if one toilet gurgles, there could be similar issues with others. To check for this, have a helper observe other toilets in the home to see if they react when you flush one.
How To Fix a Bubbling Toilet When the Shower Is Running
Clogged vent pipe
Unclogging a vent pipe typically involves inspecting the line from the roof and removing any obstructions. This is often better left to a pro, but can be a DIY fix with the right safety precautions. Read more about unclogging a vent pipe here.
Clogged drain pipe
Shower or tub drain
Avoid harsh chemical drain cleaners, which can damage pipes. Try these methods instead:
Plunger: You’ll need a damp rag, a screwdriver and a shower/tub drain plunger. This is easier with two people, so enlist a helper if possible.
- Loosen and remove the drain screen with the correct screwdriver.
- Position the plunger over the drain.
- For tubs, hold a damp rag on the overflow drain.
- Complete 10 to 15 rigorous plunges on the floor drain.
- Run hot water down the drain.
- Repeat if necessary.
Drum auger: If the drain is still clogged, try a drum auger, or snake. A drum auger features a coiled wire with a handle and crank for breaking up plumbing obstructions. You’ll also need a screwdriver.
Follow these steps to snake a shower:
- Use the correct screwdriver to remove the shower drain cover.
- Insert the snake, crank the handle to send it down the drain, and keep going until you hit resistance.
- Retract the wire to remove the clog.
- Replace the drain cover.
Snake a bathtub drain by entering through the tub’s overflow above the floor drain, following these steps.
- Use a screwdriver to loosen the overflow cover.
- Remove cover, rod and stopper, and set aside.
- Insert the end of the auger into overflow and feed into the pipe to remove the clog.
- Retract the wire and replace the stopper, rod and overflow cover.
If you’re not comfortable removing the overflow yourself, hire a plumber or purchase a disposable plastic drain snake. Keep in mind, these methods only remove clogs near the tub.
Toilet drain
Toilets can become clogged in the trapway, the curved part of the base near the back of the fixture. A plunger is usually effective at removing clogs found here. For clogs deeper in the toilet drain line, you’ll need a toilet auger.
Plunger: For this you will need a toilet plunger and some elbow grease.
- Position the plunger over the outlet at the bottom of the toilet bowl.
- Do 10 to 15 vigorous plunges to remove the clog.
Toilet auger: If the bubbling continues, try a toilet auger, or snake. Toilet augers usually come with a rubber sleeve that prevents scratches to the porcelain bowl. Wear protective gloves and wash the auger when finished.
- Insert the end of the flexible snake line by hand into toilet bowl outlet.
- Crank the auger handle to feed the line further into the toilet drain.
- Stop when you feel resistance and retrieve the line to remove the clog.
If these steps haven’t fixed the problem, Duda recommends hiring a drain company to clean and flush out the drains.
Sewer line
Duda recommends contacting a drain cleaning company to use specialized tools like cameras and extended electric augers for clearing clogged lines. Professionals can effectively address issues caused by tree roots or damaged pipes, providing expert diagnosis and repair.
Maintenance and Prevention Tips
By following these maintenance and prevention tips, you can reduce the risk of clogged drains and air vents in your home plumbing system.
- Use drain guards: Drain guards or screens in sinks, showers and tubs catch hair, soap scum and other debris before it enters the drains.
- Be mindful of what you flush: Only flush toilet paper. Never flush non-biodegradable items like wipes, cotton balls or sanitary products.
- Regularly clean drains: Use a natural drain cleaner or a mixture of baking soda, vinegar and hot water to clean drains periodically. This prevents buildup and keeps drains flowing freely.
- Trim back overhanging branches: Prevent pine needles and leaves from entering vent pipes by cutting back branches that extend over the roof, or install a vent pipe screen.
About the Experts
Alexander Siv owns Amherst Heating and Plumbing in Amherst, Massachusetts. He has a master plumber’s license in Massachusetts and more than 10 years of plumbing experience.
Jason Duda manages Boulanger’s Plumbing and Heating in Easthampton, Massachusetts. He holds a masters plumber’s license in Massachusetts, Connecticut, New York and Virginia, with 25 years of experience.
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