Bubbles coming out of a toilet's drain indicate a problem with the plumbing, since air should not be escaping through the tub's drain or any other drain in your house. Clogs in your drain pipes or even the vent pipes for your house's plumbing will lead to such problems, some of which you can remedy yourself.
Your toilet and shower's drain pipes start off as separate lines, but further downstream they connect together as they and the other drains in your bathroom feed into a larger drain pipe. Problems with one drain in the bathroom, as well as problems with the larger drain pipe, may lead to problems with other drains in the bathroom. Bubbles in a toilet's drain indicate a problem with the bathroom's drain system.
The main drain pipe that connects up to all of the drains in your bathroom also connects to a vent pipe. This vent pipe allows the sewer gasses present in the pipe to escape up and through the house's roof, keeping the gasses from entering the inside of the house. The vent pipe also maintains an equal amount of air in the drain pipes, keeping water levels in the drains at a constant.
A partial clog in the toilet's or larger drain line may lead to bubbles coming up through the toilet's drain line. A partial clog will trap air behind it, making removing the clog more of a challenge. Disturbances in the line, such as water washing down the shower's drain, will cause some air to escape from behind the partial clog, producing bubbles. Removing the toilet and feeding an auger down the drain pipe may knock free a partial clog and stop the bubbling. A larger clog even further down the line may to be blame for the bubbles. Contact a plumber for help with larger clogs.
Vent Pipe Clogs
You must climb onto your house's roof to access the vent pipe openings, allowing you to see if the pipes are clogged. Remove any clogs you see using a drain auger or by spraying water down the pipe using a garden hose. Run water down the vent pipe if you do not see any obstructions and listen to hear if the water drains down the pipe. If you cannot see obstructions or cannot remove ones you do see, call a plumber for additional help.