Toilet Backing Up Into Bathtub/Shower? Fix it Now!

Last Updated on January 7, 2022 by toilethaven

Why is My Toilet Backing up into My Bathtub/Shower?

It is one of those things that rarely happen but when they actually happen you almost don’t believe it. You flush your toilet but instead of the waste flowing down through the drain to the city’s sewer lines it backs up through your bathtub or shower drain.

If your toilet is backing up to your bathtub or shower, it is a sign that your sewer line is clogged. If you are on a septic system it could be as a result of a full septic tank. Since the toilet and the bathtub share the same sewer line, if it is clogged waste from the toilet will have nowhere to go than back up through the tub.

Sometimes it is the main house drainpipe (also known as a drain stack) that is clogged and not necessarily the sewer line.

But why would a bathtub/shower back up after flushing the toilet? Why doesn’t the waste back up through the toilet bowl?

To have a good understanding of your house’s plumbing, think of it like a tree. A tree has one big trunk and many branches. The tree truck in this scenarios is the main house drain while the branches represent each fixture’s drainpipe.

The main house drain line is then connected to the sewer line buried in your yard which will then drain the entire house’s waste to the city sewer line at the street or to a septic tank.

When the main house drain or sewer line is clogged, the waste cannot flow out to the city’s sewer lines and therefore the waste backs up through the drain with the least resistance.

If your toilet is backing up to your bathtub, turn off water to the whole house and contact a licensed plumber immediately. Do not attempt to open the sewer cleanout or use chemicals to clear the clog. Sewer line clogs are best left to professionals

The bathtub/shower drain has less resistance than the toilet drain. This is because of the water at the bottom of the toilet coupled with the design of the toilet trap acts as a barrier.

If a toilet that backs up to the shower/bathtub is not fixed fast early enough, the waste will start backing up through all of the house drains which could flood your house with sewage.

What Causes a Sewer Line/Drainpipe to Clog?

If your bathtub or shower backs up when you flush the toilet, almost always it is because your sewer line or main house drain is clogged. The drain could either be partially or fully clogged.

When the main house drainpipe is partially clogged, the bathtub/shower will back up then the water will drain slowly after sometime. If it is fully clogged, the bathtub/shower drain will back up and not drain at all. You will therefore have a lingering and awful sewage smell in your bathroom.

But what causes the main house drain to clog in the first place?

1. Flushing objects that should not be flushed

If it is not liquid, human waste or toilet paper then it probably should never be flushed down a toilet. Too much toilet paper however also responsible for clogging toilets most of the time.

Objects like toys, combs, diapers, feminine sanitary products, hand towels among others have been pulled out of toilet drains so many times. Most of these objects luckily don’t make it past the toilet trap due to its shape.

Some of the objects however manage to negotiate their way past the toilet trap and into the main house drains where cause a clog. Young kids are especially notorious for throwing stuff down the toilet so if you have them in your house you need have a conversation with them about it.

2. Tree roots


Tree roots can extend quite far from the tree itself in search of water and support. As part of their adaptation, tree roots will naturally grow towards a water source.

If your house drain has a weakness or a small leak, the tree roots will patiently make their way into it and with time cause a major obstruction that will prevent your waste from flowing out resulting in the toilet backing up in your bathtub or any other fixture in your house.

3. Mineral deposits

If you live in an area with hard water, then it is very possible that pipe scale will form inside your house drains as the minerals present in the water accumulate with time. The mineral mostly responsible for this is calcium.

Apart from your drains, the mineral deposits can clog your toilet bowl rim holes and siphon jet. If you therefore have a slow flushing toilet as result of minerals deposits in the rim holes, you will also most likely have pipe scale in your drainpipe resulting into a toilet backing up into other house fixtures.

4. Hair and Soap Scum

While taking a shower, we lose some hair that is washed down the drain. Soap scum especially in areas with hard water can help to bind the hair together.

Although the main house drainpipe is quite wide, when the hair and soap scum meets up with fats, oils and grease from your kitchen sink the drain will eventually clog.

5. Pouring Grease Down the Drain

Another thing that causes sewer lines to clog is grease. Grease will solidify inside the sewer line and form a clog that will restrict the flow of waste.

What is worse is that grease will combine with other substances in the wastewater like calcium to form a solid clog that is almost impossible to break down.

Most people believe that pouring grease down the kitchen sink drain is ok provided you follow it up with hot water. The truth of the matter however is that the grease will cool down, coalesce and form a clog.

What you should do after cooking using grease is to let it cool then pour it in sealable bags and trash it. You can as well drop it in recycling plants.

How to Fix a Toilet that Backs Up into a Shower/Bathtub

Needless to stay, you can’t live in a house where every time you flush the toilet the waste backs up through the tub or shower drain. You will need to fix it and fast. The solution might be an easy one or a very complicated and expensive one depending on what is clogging your drain.

You should start with the easiest solution and upgrade as the problem becomes more difficult to solve.

1. Turn off Water to the House

Needless to say, the water backing up to your bathtub is contaminated with germs which can make you and your family ill. The first thing you therefore need to do is secure the house by making no more waste is backing up.

The way to do that is by turning off water to the entire house. That means no one will take a shower, flush a toilet or run the washing machine or dishwasher.

To locate the main house shut off valve, head to the basement and look for it very close to the water heater on the side facing the street. If you find turn the wheel all the clockwise but if it is a ball valve turn the handle so that it is perpendicular to the pipe.

In some houses, the shut off valve is on external wall where the service line emerges from the ground. It will however always be on the side facing the street.

Do not forget to turn off the hot water shut off at the water heater as well. Remember the water heater is still full of water.

2. Plunge the toilet

In this case you will need 2 plungers. One flat-cup plunger to seal of the bathtub/shower drain and another bell-shaped plunger to plunge the toilet.

The bell-shaped plunger is the best one to plunge a toilet with since the bell will perfectly fit into the toilet bowl outlet. If you don’t have another plunger for the bathtub you can try and be innovative.  The idea is to completely seal off the shower/tub drain.

  • Have a helper seal the bathtub/shower drain with the plunger or anything else and press down firmly.
  • Flush the toilet and immediately start plunging. In order to plunge effectively, the water in the bowl has to be high enough to cover the plunger cup. Flushing the toilet will also creating more pressure in the drain.
  • Plunge aggressively and check if the situation is improving.

If you don’t seem to be making any inroads with the plunger, it is the time to upgrade to a toilet auger.

3. Snake the Toilet


A toilet auger is a long flexible cable with a spring-like head and cranking handle that you push through your toilet drain to unclog it. Most toilet augers are between 3 to 6 feet long.

Toilet augers have a plastic U-shaped protective guard that helps you prevent scratching your toilet while using it. Prior to inserting it through the toilet bowl outlet, pull the cable all the way back until the auger head is touching the guard.

Insert the auger head gently without touching the inside of the bowl and position the guard at the bottom of the bowl outlet facing upwards. Now start feeding the cable down the drain by cracking the handle clockwise.

When you come through a resistance, crack the handle in the opposite direction and then clockwise again until you go past the resistance.

When the entire cable has been fully used up pull it out by cranking the handle counterclockwise. Again remember to be careful with auger head lest it leaves some very ugly marks on your toilet bowl.

If you went all the way down with your toilet auger without encountering any resistance, then it means the clog is way deeper in the drain.

 In this case you may want to hire or borrow a longer motorized toilet auger. This augers can reach a distance of up to or more than 100 feet.

If you have never used an auger before and you are not sure that you will not scratch your toilet bowl, the best idea is to remove tour toilet first. Removing and installing your toilet is fast and easy.

Another advantage of removing your toilet is that you will have a chance of working on the drainpipe directly which will be more effective.

In case you decide to take this path, this is how to remove a toilet. Just remember to buy a new wax ring since wax rings cannot be reused.

4. Call in an Expert

Sometimes despite your best efforts you will just not fix a toilet that’s backing up in your tub/shower on your own. Calling in a professional plumber will help you fix the problem quickly although it will be expensive.

A plumber will have more experience and sophisticated equipment. Sometimes they will even need to run a camera down the drain to specifically see what’s clogging it.

Most people will be tempted to open the sewer cleanout and see if they can clear the clog from there. Don’t try that.

If water is backing up from the bathtub, it means the vertical section of pipe is full of raw sewage which you do not want to flow out first from the cleaonout.

What you can do is hire a motorized auger and climb to the roof of the house and snake the sewer line via the plumbing vent. Alternatively, you can pull out the toilet and snake the line from there.