If you’ve noticed gurgling sounds or bubbles coming from your toilet when your washing machine drains, you’re not alone. This strange phenomenon is actually pretty common in homes with older plumbing. The good news is that while it may be annoying, it’s usually not a sign of anything seriously wrong.
Backflow from Your Sewer Line
The main reason bubbles come from your toilet when the washing machine drains is due to something called backflow. Essentially, when a large volume of water like that from the washing machine flows out all at once, it creates enough force to temporarily reverse the flow in nearby pipes.
This allows air, water, and even sewage from the main sewer line to back up into pipes they’re not supposed to be in…like the ones behind your toilet bowl. The air and water erupting from those pipes then forms bubbles in your toilet.
Venting Issues Make It Worse
Backflow into a drain line can happen on its own. But usually another factor makes the problem worse: insufficient venting. Vent pipes let air in and out of drain lines so water can flow freely towards the main sewer line.
Without proper venting, drain lines form airlocks when large volumes of water try to flow out. This intensifies that sudden reverse flow of water searching for air, carrying sewer gases back with it.
It’s a Temporary Annoyance
The good news about all those gurgling noises and bubbles, though, is they tend to be temporary. That reverse flow and back up of air and water usually only lasts as long as a major appliance like the washing machine is still actively draining a large volume.
As the water level from the washing machine drum empties, pressure in the pipes usually equalizes, water starts flowing normally again, and bubbles from your toilet subside.
Why Is This Happening Now?
If you’ve lived in your house for years without bubbles in the toilet but are now noticing them when the washing machine runs, a few things may have changed recently.
Deterioration Over Time
Plastic pipes and gaskets controlling flow between drain lines can deteriorate with age and simply not work like they used to. What for years had been an air-tight passage between pipes can develop leaks, making backflow issues more likely even with normal water usage.
Heavier Usage
Has your household gone from smaller laundry loads twice a week to maxing out the washing machine daily? The frequency and volume of water flowing through pipes has increased, making temporary backflow more likely.
New Washing Machine
Sometimes a new washing machine has higher water volume ratings than the previous one. More water flowing out at once amps up pressure swings and risks of backflow if plumbing isn’t designed to handle large volumes.
Clogged Vents or Drainage
Finally, your plumbing vent pipes or main sewer drainage line could have developed clogs from debris, roots, grease buildup, or other issues over time. Restrictions make it easier for water to reverse flow and start bubbling up drains.
What Can I Do About Bubbles in My Toilet?
Don’t panic – a few bubbles making noise from your toilet during the spin cycle likely aren’t a plumbing emergency or health hazard in your household. And there are a few easy ways you may be able to lessen the annoyance on your own.
Check for Blocked Vents
Get on your roof or access attic space and inspect vent pipes coming up from drain lines. Clear any debris from the openings so air can freely flow. This may be enough to resolve a lot of gurgling bathroom annoyances.
Install a Backflow Valve
At the main sewer line exiting your house you can install a device that only allows wastewater to flow in one direction – out to the city sewer system. This will prevent air, water, and sewage already in the main lines from backing up into pipes around toilets whenever water flows strongly the other way.
Upgrade Old Pipes and Connections
If pipes and gasket rings connecting fixtures and drains are outdated or deteriorating, an overhaul by a plumber can not only reduce bubbling issues but also prevent leaks long term. Make sure connections between pipe sections are sealed tightly without gaps.
Improve Venting
In some cases, simply clearing blocked roof vents isn’t enough – the entire home’s venting system isn’t adequate. Have a plumber assess if additional vent pipes should be added, or existing ones lengthened, to equalize pressure better when drains flow heavily.
Bubbles Aren’t Necessarily Harmful, But Still Worth Addressing
While occasional bubbling during laundry isn’t considered a health issue or sign of critical drainage failure, it’s still a good idea to have a professional plumber inspect if simple DIY fixes don’t resolve the issue.
Persistent bubbles and gurgling could be a clue your pipes have deterioration or clogs that may one day lead to blocked drains, leaks, and even sewer gases entering living spaces if left unaddressed. Catching minor drainage issues early makes repairs simpler.
And even if it isn’t a huge hazard, who wants to deal with a loud, gurgling toilet every time laundry day comes around? Having a plumber identify root causes of bubbles now and make appropriate upgrades can restore peace and quiet to your bathroom for good.
References
American Society of Plumbing Engineers. “Drainline Transport Issues.” ASPE. https://aspe.org/drainline-transport-issues
Villalpando Mitchell, Angie. “Why Is My Toilet Bubbling When My Washing Machine Drains?” Angi. May 31, 2022. https://www.angi.com/articles/why-is-my-toilet-bubbling-when-my-washing-machine-drains-6441894.aspx
Ramsey, Dan. “Toilet Bubbling When Washing Machine Runs.” Property Safety. June 1, 2022. https://propertysafety.com/toilet-bubbling-when-washing-machine-runs/
Laura has had an enthusiasm for laundry ever since she was a teenager experimenting with wash cycles. She went on study textile science in college before working in product testing.
Soon, Laura found friends and family constantly asking her laundry advice, realizing she had become an unofficial laundry guru. The questions kept coming in, so Laura decided to start sharing laundry tips online to help more people. The enthusiastic response led her start the blog “Laundry How”.
Now in her late thirties, Laura uses Laundry How to tackle all kinds of laundry topics – stains, fabric care, detergents, and more. She provides advice from both her studies and experience testing techniques out firsthand. Laura continues to grow an engaged community of laundry learners, feeling fulfilled empowering people to make laundry an easy, confidence-building ritual rather than a dreaded chore.