The drainpipe for your toilet and the drainpipe for your bathtub start off separately from one another, but the pipes join together with all of the other drainpipes in your bathroom. A problem with the main drainpipe in your bathroom will lead to water from one drain backing up into the other.
You first need to plunge not only the toilet but also the bathtub’s drain. Likely a clog has lead to the backing up, and the clog may not sit too far down the drain line that plunging will not dislodge the clog material.
Use a regular plunger on the bathtub’s drain, once you have removed the stopper or drain cover. Use a funnel-cup plunger in the toilet’s drain, since the curving underside of the funnel-cup fits the drain’s contours better.
A drain snake will feed down the drain line, coming into direct contact with the clog itself. Use a toilet snake with the toilet, and feed it all the way down the toilet’s line as you spin the handle clockwise.
Spin the handle counterclockwise as you pull the snake back out of the toilet’s drain. Remove the screws that hold the bathtub’s overflow drain cover in place and pull off the cover.
Feed the drain snake down the overflow tube and push it through the curving P-trap pipe below as you spin the crank on the snake’s body clockwise. Spin the crank counterclockwise as you pull the snake out through the overflow tube again.
Clear Vent Pipe
Sometimes a clogged vent pipe will cause water from the toilet to back up into the tub’s drain. Climb onto the roof and locate the vent pipe’s opening, which will sit over the bathroom.
Shine a flashlight down the vent pipe to look for obstructions. Pull out any obstructions that sit near the top of the vent pipe, using a retrieval tool.
Use a drain snake to push out any accumulation of debris, or spray your garden hose down the vent pipe.
Deep snaking the toilet’s drain will allow you to reach more serious clogs down the drain line. You must first shut off the water to the toilet and then remove the nuts holding the toilet to the bolts in the base.
After you remove the toilet, feed a 25-foot-long drain snake down the waste pipe in the floor as you spin the crank on the handle clockwise. Do not retract the snake until you have fed the entire line down the drain pipe, and then spin the crank counterclockwise.
If the problems continue, contact a plumber for help.