What Causes a Drain to Clog Up & Back Up Into the Bathtub?

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An occasional snaking out of a bathtub drain can help prevent backups in the future.

For most homeowners it's an inevitable fact of life that a drain in their home will eventually become clogged. Unfortunately, and depending on which drain or section of piping in the house has become clogged, backups into the bathtub could result. In many cases, hair clogs the tub's drain, which in turn causes water to back up. Cleaning out the drain or applying a natural drain cleaner can help.


A home's water piping system has several types of outflow drains. The ones homeowners are most familiar with are sink, bathtub and shower drains. Outside the house, essentially two other types of drains exist. Plumbing professionals call these "clean outs." They're part of the home's main sewer line, which runs between the home and the large-scale water and sewerage systems serving each house in a town or municipality.


When drains inside a home become clogged, obstructions in their p-traps are almost always the culprits. P-traps are usually beneath a sink or tub. For tubs, large amounts of hair and a lack of occasional drain cleaner application are usually what lead to the situation. In sinks, organic material such as grease, leftover food or objects such as forks or spoons can be likely causes.


Another type of problem in a home's piping and drain system can happen when the main drain pipe becomes obstructed or clogged. Because tub and shower drains sit lower than more highly elevated sink drains, backups tend to hit bathtub and shower drains first. In those cases, what's called "sink sewage" -- the wastewater that's drained from sinks in the house -- can end up in the bathtub. Air can also get into the main drain, causing backups.


It's usually not recommended that a harsh chemical de-clogging agent be used to clear clogged drains and pipes. Rather, periodically pouring a homemade drain cleaner down a bathtub or sink's drain will work just as well. Pour a cup of baking soda down your drain. Follow that with a cup of vinegar and then plug the drain hole. Wait 30 minutes and then flush with hot water. Severe clogs could require a plumber's snake.

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Tony Guerra

Tony Guerra served more than 20 years in the U.S. Navy. He also spent seven years as an airline operations manager. Guerra is a former realtor, real-estate salesperson, associate broker and real-estate education instructor. He holds a master's degree in management and a bachelor's degree in interdisciplinary studies.