Toilet Backing Up into Tub & Sink: Causes & Quick Fixes

The sewage line in your home is connected to all your water and waste outlets in the house from the bathtub to the shower, the sink, the toilet, and other pipes. Hence, if you notice water backing up from the toilet to the tub or sink, then the passageway from the drain pipe to the main sewer is blocked and has a clog.

More often than not, this isn’t a small issue, especially if it has to do with the main sewer line, and you may need to call in a plumber. But before we get ahead of ourselves, there are quick fixes you can try to see if they can unclog the pipes.

What Does it mean to Back Up?

Backing up means that instead of the water or waste flowing through the pipes to the sewer line, it either goes back to the original place which is the toilet, or finds an alternate route say to the bathtub or sink. The drains where the wastewater was to be transported are obstructed causing the water to go backward instead of towards the sewage line.

Causes with Fixes

As mentioned in the introduction, water backing up from the toilet to the sink and tub is a classic sign of a clog. So your next cause of action is to try and look for the location of the blockage.

Mild Blockage

The toilet is the first water outlet to experience clogs in the house. More often than not, if the drain in the house is obstructed, it will also be the first to show, for example, you may notice a high water level in the toilet bowl or overflowing water when you flush.

If this is the case for you, you can do the usual toilet unclogging techniques such as plunging, using a toilet auger or snake, plus other methods. If you choose to use a plunger, use the closet/ flange plunger because it will exert more suction to the toilet clearing and clogs.

The snake will also do a great job of reaching deep into the drain pipe to remove any waste.

If both these solutions don’t help, you may be experiencing a clog in the main sewer line.

Sewer Line Blockage

This is a more severe type of clog that means you’re probably going to need a plumber to fix it up, but before you jump on the call. Check for these classic signs of a blocked sewer line.

  • The wastewater may drain, but slowly.
  • The clog is affecting all the other water outlets such as sinks, tub, and the shower.
  • Water backing up from the toilet to the other outlets (tub and sink) every time.
  • Toilet bubble and gurgles which you can also hear in the bathroom sink and shower.
  • The toilet overflows or all your toilets don’t seem to work

Now that you have confirmed that you indeed have a blocked sewer line. You ought to fix it as soon as possible.


There are two ways you can fix the drain, they both involve cleaning the main sewer drain;

  • Chemical cleaning
  • Mechanical cleaning
Chemical Drain Cleaning

Chemicals act as enzyme-based drain cleaners that will get rid of any form of the clog by degrading the waste faster than it originally would. You will need to use different types of chemicals to clear the clog. Here’s a step by step guide;

  1. Purchase a chemical drain cleaner such as copper sulfate, which comes highly recommended by professional plumbers as it can dissolve even tree roots.
  2. Measure about a cup of the chemical and pour it into the toilet bowl.
  3. Flush it down the toilet and let it stay for about 30 to 40 minutes.
  4. Repeat the process as it needs to be done at least three times to clear the clog.

Even though copper sulfate is a recommended cleaner, it’s not very safe for the sewer as it may cause reactions with the pipes especially if you don’t know the type of pipes your building has; plastic, iron, or otherwise. Moreover, this chemical is prohibited in some municipalities.

Alternative chemical solutions that could also dissolve water such as roots include chemical foams with herbicide dichlobenil. The foam works in just a few hours to clean the complete sewage system. Furthermore, it can be used to clean up the pipe scale that’s also known to cause mild blockages. Pipe scale is a mineral layer usually composed of calcium or magnesium that occurs naturally in our water.

The scale can form on any surface that meets water, including your pipes. It can easily build up and cause a blockage in your sewer line.

Mechanical Drain Cleaning

Your last resort is the use of mechanical drain cleaning which is done by pro plumbers who use specialized tools to get into the drain. They will have a mechanical auger, bigger than the ordinary snake, which is inserted in the drain. They could work from the outside to unclog the sewer line.

What happens is that they will insert the specially designed truck-mounted flexible cable in the drain and it’s fed continuously until they get to the clog. The auger will then move around to break apart the clog and the work is done.

The second tool they can use is a high-pressure water jet that will be blown into the pipes. The pressure is high enough to remove dirt and debris down there without any worries. This method is best done by proceeding as they have a better understanding of how to use these mechanical tools.

Vent Clean-up

Sometimes the vent pipe doesn’t have a clear pathway for air to pass freely. It may be blocked by tree branches, leaves, and other debris that go straight to close up the sewer line. In this case, you have to get up to your roof and clear up the vent pipe to allow for a clear path.

Prevention Measures & Tips

  • Regularly check the vent openings on your roof and clear out any dirt you may find. Avoid accumulation of dirt such as trees, leaves, and other debris as insufficient ventilation is a major cause of the blockage.
  • Invest in drain cleaners which you can use to clear any blockage in the drain before it becomes worse. You can also add the cleaner to your toilets, bathrooms, and sink outlets simultaneously to clear the path to the sewer line. Just don’t go. For harsh chemicals as they could easily damage the pipes without having done any good.
  • Check that you’re only flushing down biodegradable waste such as tissue paper. Anything else could easily cause blockage and accumulation could happen faster than you know (in a matter of hours). This means avoid disposing of wet wipes, tampons, and other sanitary items
  • Avoid pouring fatty waste such as grease in the drain as well as it will harden once cooked down causing a block again
  • Avoid disposing of hair in the drain as well. They too can accumulate in the drain causing a blockage.

These preventative tips emphasize on avoiding a clog before anything else. As you have read above the clog can be as severe as a sewer blockage which affects all the drain systems in the house, hence the backing up.

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