How to Unclog a Toilet That’s Backing Up Into the Bathtub?

Written by

Paulk Webb


Freddie J. Hagopian

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how to unclog a toilet that's backing up into the bathtub

Imagine sewage coming up through the bathtub or shower area that is supposed to be clean. Aside from being unsanitary, it’s baffling how this happens within the pipes.

Thinking about how toilet water reaches the bathtub drain may sound confusing, but this is actually a common and easily fixable problem of clogs accumulating that occurs down your drain system.

Specifically, a clog below the main drain line causes the normal flow of toilet water to be disrupted and rerouted to other nearby pipes, including the bathtub drain.

Fortunately, learning how to unclog a toilet that’s backing up into the bathtub is relatively quick and easy and would only need basic unclogging methods and items that are usually available at home.

Step-by-step to Unclog a Toilet That’s Backing Up Into the Bathtub

What to prepare:

  • Plunger
  • Toilet auger
  • Duct tape
  • Bucket
  • Pliers
  • Rubber gloves (optional)

Step 1: Close drain plug of tub and sink


In preparation for plunging the toilet, the drain stopper or drain plug of the bathtub and sink should be closed shut.

This is done to direct the pressure from plunging towards the clog instead of just letting the sewer air and water coming up through bathtub drain to exit on the nearest openings.

Step 2: Cover other exit points with duct tape


In addition, to ensure a more efficient plunging later, cover the overflow opening of both bathtub and sink, the shower drains, as well as other possible routes, with duct tape.

Make sure that all the exit points of both air and water are blocked. Again, this ensures that the pressure you exert is strong enough and will be directed to dislodge the blockage.

Step 3: Plunge that clog down


Start to unclog toilet and bathtub drain by using the good old plunger method. This is the most common remedy when flushing toilet water comes up in tub.

Place the plunger’s suction on the toilet bowl’s opening and pump with force repeatedly. You may check if there is progress by flushing the toilet afterward. Repeat plunging until you see improvements.

Since you are pumping continuously, the duct tape applied earlier can come off due to all the pressure exerted. Seal off and add more layers of tape, if necessary, before plunging again.

Step 4: Insert toilet auger on cleanout fitting


If sewer water is still backing up into the shower even after plunging, you may want to try using a toilet auger. Wear rubber gloves, as this can be a very messy method.

Normally, you would insert the coil into the toilet opening and crank the lever to push the pipes down further. Once you feel resistance, you’ve already reached the possible clog.

But as mentioned, the obstruction could be far down the main sewer line, so it would be difficult to reach it through the toilet only.

It is recommended to find a cleanout fitting around your house. This provides easier access to the main sewer line where the clog may have accumulated.

Use pliers to open the fitting. Be careful, as sewer water may be spewed out after unscrewing the cap. It is best to prepare a bucket to avoid making a stinky mess.

Insert the auger and crank until you break up or push down the clog. You will be able to get rid of sewer backup in bathtub once the blockage is completely removed.

Optional Step: Use Gravity in Your Favor


Aside from the methods mentioned above, you may also try using the weight of water plus gravity to dislodge that possible clog in your main drain line.

Turn on the source of hot water into the bathtub and let as much water to drain down the pipes. Both the temperature and amount of water can help in loosening up that blockage.

Shortly after this, dump hot water in the toilet and let gravity do the work again. Unclogging your pipes may be easier with both toilet and tub drain acted upon by the weight of water flushed down.

At the same time, you may also incorporate plunging as you pour water on either toilet or bathtub drain. This adds more force needed to dislodge any accumulation down your sewer line.



Why is my toilet backing up in my tub?

A clogged toilet and bathtub pipe connection in the main drain line blocks the normal flow of toilet water, causing it to find an alternate route – one of which is the bathtub pipes.

A common pipe layout for homes is that all water fixtures – toilets, sinks, tubs, showers – are connected to the main drain line where all forms of waste travel down to the sewer.

And this main drain line, connected to the vent pipe sticking out of the roof, is also susceptible to clogging. Blockages here usually cause common draining problems.

A clog specifically located below the point where both toilet and bathtub drains are joined causes the problem of waste water from the toilet backing up into tub.

The toilet water’s normal flow is disrupted by the presence of this blockage, and the only accessible exit point would be the nearest drain pipe, one of which is from the bathtub.

Water flows this way instead and the waste from the toilet is now backing up in the tub pipes. This is the reason for the gurgling in your bathtub drain as you flush your toilet.

What do you do when your bathtub and toilet is clogged?

It is important to switch off the water sources and avoid dumping additional water into a clogged toilet or bathtub to prevent a messy overflow.

The immediate action is to break down the clog using a plunger or toilet auger. You may also try to dissolve or loosen up the clog using various home or commercial chemicals.

If you flush the toilet and the bathtub gurgles in addition to backing up, there is definitely a clog somewhere below the point where the toilet and tub drain joins the main sewer line.

You may choose among the various ways to unclog a drain line in order to bring back the normal flow of water and eventually fix the problem of sewage coming up through bathtub drain.

How to prevent my toilet backing up in my tub?

Being mindful of things that get flushed down in your toilet and bathtub drain are common preventive measures for clogging – which is the cause of water coming up bath plug hole.

Toilet papers, hairs, soaps, sanitary products, and other foreign debris are the usual objects that accumulate within the pipes. Make sure these items would not reach the insides of the drain system.

Aside from human wastes, avoid flushing any other items down your toilet. Be cautious even with throwing tissue papers as these can accumulate and form clogs, as well.

In addition, installing hair traps or catchers in your tub ensures minimal hair residue that could travel down and possibly clog your main drain line and have your toilet and tub backed up.

Can my toilet still back up even if it’s not clogged?

A toilet backing up but not clogged in the drain pipes is still possible. The issue would be the airflow in the vent pipe connected to the main drain line.

The vent pipe enables the proper flow of air within your drain system. When this is blocked and air cannot travel normally, flow of water is affected and may cause problems, as well.

Even if there is not a clog down the pipes, your toilet can still gurgle, overflow, or back up because of negative air pressure within the drain lines – caused by a blocked vent pipe.


We have seen the adverse impacts of a clog, especially when it successfully accumulated down below the main sewer line.

But once the clog has been removed, you won’t need to stress yourself again with sewer water backing up into your bathtub everytime you flush your toilet.

Apply these basic approaches and methods on how to unclog a toilet that’s backing up into the bathtub, as well as some preventive tips to avoid formation of clogs, and there won’t be a need to hire a plumber any time soon.

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