Drain pipes that take out the toilet's wastewater are totally separate from the supply pipes, one of which brings water into the toilet. If the supply pipes are frozen, you can likely only flush the toilet one time, unless you manually add water. If the drain pipes are blocked because of a freeze, you can't flush the toilet.
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Frozen Water Supply Line
If the supply line is frozen, you'll only be able to flush the toilet once using the water already stored inside the tank. The frozen pipe prevents fresh water from flowing into the tank to refill it, and the bowl's water level will also be low, because some of the tank water is diverted down to completely fill the bowl.
If the pipes remain frozen and you need to use the toilet, get buckets of water from another source, such as a sink where pipes are not frozen. Pour cold water into the toilet tank or pour the water directly into the bowl to flush the toilet after using it.
Frozen Drain Pipes
The drain pipes are less likely to freeze, but if it does happen, don't flush the toilet or it will just back up into the bowl. Eventually, water will spill over onto the floor if you keep flushing before the water has a clear path to exit through the plumbing. One possible solution to clearing out ice in the toilet's drain pipe is to pour a bucket of hot water down the toilet drain.
Vent Stacks and Main Line
An additional consequence that sometimes arises after cold weather blows through and pipes freeze, is that a vent stack or main line gets clogged. Afterward, the toilet backs up and you can't flush it. In this instance, another fixture's drain — such as the bathtub — will also back up with water.
To fix this so that you can flush the toilet again, insert the cable of a toilet auger, also called a plumbing snake, down through the vent pipe on the roof to reach and break up the blockage. But if cold weather has frozen your pipes, the roof may be hazardous to maneuver because of snow or ice buildup. You may want to call on a plumber for this task. To clear out a main line, insert the auger cable through a sewer cleanout.
Thawing the Pipes
In addition to pouring hot water down the drain to help unfreeze a toilet's drain pipe, you can use other methods to thaw out frozen pipes. If you don't try to unfreeze the pipes, waiting for them to thaw out on their own sometimes takes several days.
Open the sink faucets near the toilet and begin thawing the pipes as close to the open faucet as possible. For pipes inside the house, open cabinet doors that hide pipes and turn the inside heat up. If a pipe is already slightly thawed, wrap it in rags and continuously pour hot water on it. Or move a portable electric hair dryer back and forth across sections of frozen pipe to thaw them.
Christopher John has been a freelance journalist since 2003. He has written for regional newspapers such as "The Metro Forum" and the "West Tennessee Examiner." John has a Bachelor of Arts in journalism from Memphis State University.