Your bathtub and toilet connect to one another through the drain pipe system in your house. If washing water down one plumbing fixture causes gurgling in another, you need to examine the venting system, which should prevent gurgling problems. A blocked or damaged venting system can create other problems in your home, making finding the cause a high priority.
Your bathtub, toilet and every other plumbing fixture in your home attaches to a vent system through the drain pipes. These vent pipes run all the way through the house's roof. You will see the pipes coming out of the roof if you stand far enough away from the house. The vent pipes help keep the same amount of air in the drain end of the plumbing system. Every time you flush the toilet or wash water down a sink drain, water goes down the drain as well. The vent pipes replace the lost air, keeping the drain pipes running smoothly.
Look for Problems
You will need to climb onto the roof to inspect the vent pipes. Remove any objects sitting on the pipes, such as bird's nests, since they will block air flow. Shine a flashlight down each of the pipe openings to look for any objects that have fallen inside, such as tennis balls, tree leaves and twigs. Objects in the pipe do not have to close the pipe off all the way to cause problems. You may need to install a cover over the vent pipe if overhead trees are dropping debris in the pipes, since the problem will reoccur until you do.
You cannot reach down the vent pipes with your arm, since they are too narrow, but you can pull out debris using a flexible retrieval tool or other slender devices. Do not force a stuck object too much, since you may damage the vent pipe and create a new problem. Put a high-pressure attachment on your garden hose and shoot water down the pipes to wash away stuck leaves and twigs you cannot reach.
Sometimes you need to call a plumber and pay for professional help. If you cannot see any problems with the vent pipes from the roof, the plumber has the ability to create fake smoke to send through the pipes so he can locate clogs or damage in the vent pipes. Plumbers also have long augers that will reach clogs that are out of your reach.