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Water Coming Back Up Through Kitchen Sink? 4 Causes

Although it’s rewarding being a homeowner, it can also be highly stressful when unforeseen problems arise, such as water coming back up through the kitchen sink. But what causes water to come back up through the sink?

Water coming back up the kitchen sink could be due to food or debris clogging your drain, a clog in the P-trap, jamming of your garbage disposal, or a drainage issue with your dishwasher. Solutions include clearing any blockages in your drain, garbage disposal, or dishwasher and flushing your pipes.

This article will discuss some common reasons your kitchen sink might have water backing up into it and what to do if this happens. Keep reading to learn more.

1. Food or Debris Has Clogged Your Drain

A common side-effect of doing the dishes is food and gunk making their way into your sink drain.

While small amounts of food entering your drain may not be a big deal if you have a garbage disposal, without one, that debris makes its way into your pipes and has the potential to sit there and cause problems if it doesn’t get flushed out.

One such problem is that it can create a barrier that makes it impossible for water to run down your drain, meaning it backs up into your sink whenever you try to run the faucet.

The good news is that food and debris that clogs your drain to the point that water begins backing up is usually pretty near to the surface.

This means that with a bit of elbow grease and a few chosen methods, you should have no problem clearing it out.

How To Fix It

There are many ways you can go about attempting to unclog your drain, the method you choose is entirely up to you, but if you’re struggling to fix it, you may want to run through all these options before calling a plumber.

Try Plunging Your Drain

While you may think a plunger is only suitable for a clogged toilet, they’re excellent tools for unclogging drains as well.

For sanitary reasons, it’s recommended that you buy a separate plunger from the one you keep in your bathroom. Plungers like this Luigi’s Sink and Drain Plunger (link to Amazon) are specially designed for sink drains and are small enough to be stored underneath your kitchen sink when you’re not using it.

For the plunging to work, you’ll need to make sure there are at least several inches of standing water in your sink and then plunge for about 30 seconds. 

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Doing this a few times is recommended to help loosen the blockage and clear up your drain even if water begins flowing after the first plunge; better safe than sorry.

Pour Boiling Water Down Your Drain

If you have all-metal piping, you should consider running boiling water down your drain. 

Water at this high of heat has a better chance of breaking through minor clogs and melting any fat or grease that may be clogging the passageways.

Don’t attempt this method if you have PVC pipe drains. The boiling water is potentially harmful to the plastic, and you don’t want to do more damage to your plumbing system.

Pour a Mixture of Baking Soda and White Vinegar Down Your Drain

This method will only work if your kitchen sink has stopped backing up water and has drained. 

If your sink doesn’t drain on its own, you’ll need to either plunge it until water begins draining again or remove the water using a cup or bucket.

Once there’s no more standing water in the sink, pour one cup of new baking soda down the drain, followed by one cup of white vinegar.

The dissolving solution should help clear up any food or debris that has gotten trapped in your drain.

After leaving the solution for about 15 minutes, run hot water down the drain for several minutes to flush it out.

Run an Auger Down Your Kitchen Drain

If both options fail you, you can try using a drain snake, such as this FlexiSnale 18-inch Drain Weasel (link to Amazon), to clear the blockage. The FlexiSnale is affordable and long enough to reach deep into the pipes to remove build-up.

This method is only intended to clear clogs that are very near the drain’s surface, often caused by large amounts of food making their way down the drain all at once.

Use a Sink Strainer

Prevention is the name of the game when it comes to clogging your drain, and the easiest thing you can do is keep food out.

If you don’t have a garbage disposal, consider investing in a sink strainer, such as this OXO Silicone Sink Strainer (link to Amazon). It’s easy to clean and fits most drains. 

Sink strainers, like the OXO Silicone Sink Strainer, provide a screen that shields your sink drain so that any food that makes its way into your sink will clog your sink strainer rather than your pipes (source).

2. The P-Trap Is Clogged

If you look under your kitchen sink, you’re likely to see that the drain leads down to a section of pipe that is shaped like the letter “P.”

This section of piping is called the P-Trap. It’s designed to catch any food or debris that has made it into the sink drain from traveling further into your piping system and causing clogs.

When your sink won’t drain, or the water is backing up when you try to run the water, it’s often because your P-trap has functioned exactly as it was supposed to but has become clogged.

You may notice that your P-trap is partially blocked before it gets to the point that water is coming back up the sink if it begins to drain more slowly than usual.

You’ll want to address the issue as early as you notice it to avoid any unintentional water damage.

Fortunately, clogged drains are relatively minor issues that don’t typically leave any lasting damage to your home.

How To Fix It

While inconvenient and perhaps slightly gross, cleaning your P-trap is a relatively easy and quick process.

Knowing how to do this in the future is a handy skill that any homeowner should have.

Begin by ensuring your water is turned off and clearing out the cabinet underneath your sink to prevent anything from getting wet. You’ll want to set a bowl and a towel on the ground to catch any water or debris that falls when taking the pipe apart.

You’ll notice two screws at the end of your P-trap: one that connects it to the kitchen sink drain and a second one that connects it to the pipe leading into the wall. 

Unscrew both of these and remove the P-trap. Using a plumbing snake, an auger, such as this Drainsoon Auger (link to Amazon), clear the P-trap of any debris. The Drainsoon Auger is especially useful if your kitchen drain is smaller. It can also be used on other drains too, such as floor drains or bathtub drains.

You may want to ensure that the connecting pieces of pipe are clear of debris as well, so feel free to run your auger up the sink drain and into the wall pipe. 

Once your P-trap is cleaned out, screw it back onto the connecting pipes. Run hot water down your sink for a few minutes to flush the lines. 

While the water is running, look under your sink to ensure that you adequately tightened the screws and there isn’t any leaking.

Home Depot offers a beneficial step-by-step video on how to do this if you’re more of a visual learner.

3. Your Garbage Disposal Is Clogged

If you have a garbage disposal, it’s easy to feel immune to your drains clogging because of food or debris getting flushed down. However, garbage disposals bring their own potential set of problems.

When your garbage disposal gets clogged or jammed, it can prevent water from running through your pipes, causing it to back up through the sink.

Garbage disposals can get clogged for several reasons, including sending too much food down the drain at one time, dropping foreign objects into it, or a buildup of fat and grease.

Rather than pay a plumber to come out every time your garbage disposal gets clogged, try and troubleshoot the problem yourself first and see if you can remedy it.

How To Fix It

To begin, you’ll want to make sure there’s no standing water in the sink. Start by plunging the sink to rid it of moisture. If this doesn’t work, you’ll have to bail the water out using a glass or bucket.

Once there’s no standing water, you can try adding equal parts fresh baking soda and white vinegar and leaving it for 15 minutes, as you would with a standard drain, then try running the garbage disposal.

If this doesn’t work, you can also try pouring a small amount of degreasing dish soap down the drain and running cold water for several minutes. This will help free up any fat or grease residue that may be impacting your disposal’s ability to run.

You can also try pressing the reset button on the central part of your garbage disposal under the sink and manually rotating the blades, also known as the impellers, if necessary.

To do this, look under your sink and find the red reset button on your garbage disposal. Turn the disposal off, press the reset button, and then turn it back on.

If your disposal still doesn’t run, you may need to rotate the garbage disposal blades. First, turn off your garbage disposal. You can then manually turn the edges by reaching your hand or a wooden spoon down the disposal.

Turn the blades in both directions to break up the clog, turn your disposal back on and try again.

If all these methods fail, it may be time to contact a plumber to get a professional opinion.

4. Your Dishwasher May Not Be Draining

While this might seem unrelated, your dishwasher and your kitchen sink share the same drainage system.

If your dishwasher stops draining properly, this will likely have an impact on your kitchen sink draining.

Ask yourself if the only times your kitchen sink backs up with water is when your dishwasher is running.

If the answer is yes, then it’s likely that your dishwasher is the root cause of your problem.

How To Fix It

There are several simple troubleshooting steps to try if your dishwasher isn’t draining correctly.

First, look under the sink. Check and make sure there are no kinks or tangles in the drain hose that connects the dishwasher to the drain. Sometimes it’s as simple as making sure water can run through the drain hose.

If everything is looking good with your drain hose, try running the garbage disposal. 

Because many dishwashers drain through the garbage disposal, if it’s clogged or has a collection of food, making it hard for the water to run through, this may fix your drainage problem.

Lastly, if you notice that the dishwasher has standing water in it and isn’t draining correctly, consider the possibility that your dishwasher drain may be clogged. 

Try mixing equal parts fresh baking soda and vinegar and allow it to sit for 15 minutes. 

After sitting, pour hot water down the drain basket and run your dishwasher on the rinse cycle. This should free any blocks in your dishwasher drain.


While it’s always alarming to see water backing up through your kitchen sink, remember that this is likely a relatively harmless issue that you could probably fix on your own.

Typically, due to light clogging of your pipes, garbage disposal, or dishwasher, finding the root source of the blockage is key to getting an open drainage system.

Once you’ve located the source of the clog, simply follow the steps in this article to unclog your sink.

Avoid using harsh chemicals that may hurt both you and your plumber if they don’t drain all the way or your plumbing system.

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