What causes a toilet to bubble up?

Of all the fixtures in your bathroom, the toilet is the one that usually causes the most inconvenience if it begins to malfunction. Gurgling or bubbling noises from your toilet can be particularly troubling, especially if they are accompanied by a high-filling bowl or frustratingly slow drain. A bubbling toilet is an indication of several potential problems with solutions that range from a simple do-it-yourself fix to a professional plumbing job.

Inside the toilet tank, the rubber flapper is responsible for controlling the level of water inside both the tank and the bowl. When you flush the toilet, the flapper lifts and allows water to leave the bowl. If the flapper is malfunctioning, the tank levels may not be consistent. If there is too much air inside the tank and the water level is low, the tank will make a choking, gurgling sound each time you flush as air bubbles pass through the flapper and into your plumbing. Fixing a malfunctioning flapper is a simple repair; usually a flapper malfunctions because the lifting mechanism is caught or knotted, but you may also need to replace the rubber flapper if it looks deteriorated.

A blockage in any part of your plumbing often manifests as gurgling or bubble sounds while your toilet drains or refills. The exterior vent pipe that provides an outlet for air in the pipes may become blocked by yard debris, trapping the air and causing bubbling. Clearing the offending debris should allow clear passage of air. If your vent pipe is flexible, ensure that there are no kinks in the pipe that would trap the air. Toilet clogs also cause bubbling as the water struggles to drain and returns to the bowl; plumbing snakes are useful tools for removing clogs. If the bubbling is consistent, the pipes in your plumbing system may be too small to allow water to pass freely through; replacing the pipes will fix the problem though replacement may be costly and time consuming.

Cracks in either your plumbing pipes or your toilet allow air into the system. The trapped air often makes it way back into the bowl, causing bubbling even when you aren't flushing or filling the bowl. Small pools of water near the bowl or on walls and floors through which the plumbing passes are good indicators of a crack that may be causing the bubbling. Most cracks are small enough to fix with sealant, but larger cracks may require replacement parts or professional repairs.