Washing Machine Backing Up into Sink: Causes, Fixes, and Prevention

washing machine backing up into sink

Are you experiencing a washing machine backing up into sink? Then you are in a messy and frustrating situation. Needless to say, when washing machine drain into sink can cause a lot of damage if you do not take immediate action. It can lead to damage to both the washing machine and sink.

However, this common plumbing issue occurs when water from the washing machine overflows and enters the sink drain pipe, causing water to gush out of the sink. Several factors, such as clogged drain pipes, venting issues, plumbing configuration, or other system problems, can cause this issue.

Why this issue needs attention:

  1. It can cause water damage to the home, seeping into walls and floors and resulting in expensive repairs.
  2. Washer drains into the sink, causing inconvenience, making it difficult to use a sink for other purposes, and producing an unpleasant odor.
  3. Lastly, the dirty water from the machine may contain chemicals, bacteria, mold, and other harmful substances. This contaminated water can enter the sink and the plumbing system of the home, posing a risk to health and hygiene.

But don’t worry, there are ways to fix this issue.

Today, we will discuss the causes of this issue, solutions to resolve it, and prevention methods to avoid it from happening again.

Causes of Washing Machine Backing up Into Sink:

Many homes share the same pipeline to drain water for the kitchen and washing machine. No matter the problem occurs in the kitchen sink or washing machine pipeline. The result is sink backs up when the washing machine drains. In that case, we have found the seven main reasons that can be the culprits for washing machine backing up into sink.

Let’s find out what happened in your case.

Problem 1: Clogged Pipeline

When a kitchen sink and a washing machine share the same drain pipe, it often clogs the pipeline. The primary cause of this issue is the accumulation of grease, soap, oil, food debris, cleaning detergent, and other collects in the pipe with time.

All these materials accumulate in the drain pipes, causing a blockage and preventing water from flowing through the line. As a result, it leads the washing machine to drain into the sink or even overflow from the washing machine.

 Problem 2: Incorrect Plumbing Installation

At the time, the plumbing system of your washing machine and sink is not installed correctly, which can cause water to flow in the wrong direction, leading to a backup.

When the washing machine drain hose is connected directly to the sink drain pipe, it can overload the system. Similarly, if the sink drain is not vented correctly, it can also cause the water to back up.

Whether your washing machine may need to be configured correctly or the drain may be too high or too low, preventing water from flowing out properly.

Problem 3: Faulty Darin hose or Malfunctioning Washing Machine

Find out if the drain hose that connects the washing machine to the sink has become damaged or worn out. Because it is another reason for washer drains into sink.

Moreover, a malfunctioning washing machine can also cause a backup. For example, if the device is not draining correctly, it can cause water to back up into the sink.

Problem 4: Inadequate Venting Strait

The plumbing in your home needs proper ventilation to function correctly. If there is inadequate venting in your plumbing system, it can cause water to back up into the sink when you run your washing machine.

The vent generally connects your plumbing system to the outside and can be blocked by leaves, debris, or bird nests. These blockages can prevent air from flowing through the system, causing washer drains into the sink.

Problem 5: Insufficient Drain Size

The insufficient drain size is a vital cause of the washing machine backing up into the sink. When the drain size is too small to handle the amount of water and detergent used, the water cannot drain fast enough, leading to an overflow and eventually backing up.

A standard washing machine drain pipe has a diameter of 2 inches. Whereas the pipeline’s diameter is too small, or if the drain line is too long, it causes water to back up into the sink. It is especially true if the washing machine uses a lot of water or is on a high spin cycle.

Problem 6: Malfunctioning P- Trap

The P-trap is a necessary component of any drain system typically attached to the drainpipe. A curved section of pipe below the sink prevents sewer gases from entering the home and allows water to drain rightly.

Eventually, a malfunctioning or incorrectly installed P-trap can cause washing machine water to go back into the sink.

Another possible cause of a P-trap malfunction is a blocked vent pipe. The vent pipe also allows air to enter the drain system, preventing water from being siphoned back into the sink.

Problem 7: Low Water Pressure

The low water pressure in your home can prevent the washing machine from properly draining water, causing it backing up into the sink. It can happen due to various factors, including clogged pipes, a malfunctioning water pump, or a problem with the main municipal water supply.

Signs that Your Washing Machine is Backing Up into the Sink:

Generally, four sing help you to understand your washing machine backing up into sink. By recognizing these signs early on, you can take action to prevent further damage.

1. Gurgling Sound Coming from the Sink Drain:

You can hear a gurgling sound from the sink drain while running your washing machine. It happens because air gets trapped in the drain pipe, creating a gurgling sound. The sound shows that washing machine water is backing up into the sink.

2. Slow Draining:

If you see your sink draining slowly after using the washing machine, then it could be a sign your sink backs up when the washing machine drains.

3. Foul Odor from the Sink:

If your sink has a foul odor, it could be a sign that your washing machine is backing up into the sink. When the water from the washing machine cannot drain correctly, it can create a buildup of bacteria and other contaminants in the plumbing system. It can lead to a foul odor coming from the sink.

4.  Water Overflow in the Sink:

Finally, when the water from your washing machine overflow into your kitchen sink, it is a significate indication that something is wrong with your plumbing system. Besides a clear sign, your washing machine backs up into the sink.

How to Fix Washing Machine Backing Up into Sink:

We have shown you basic and advanced techniques to fix the water backing issue. Let’s begin with the primary method and see if it is helpful.

Method 1: Use of Plunger

One of the first things you can try to fix a washing machine backing up into the sink is using a plunger or a drain snake. It is a basic solution that can help remove any blockages. Insert the plunger into the drain and move it up and down vigorously to clear the blockage.

A plunger can clear a clogged drain if the obstruction is not too deep within the pipes, which means the blockage isn’t too far into the pipeline.

However, first, fill the sink with enough water to cover the head of the plunger. It will help create a needed suction. Next, place the plunger over the drain to form a tight seal. Ensure that the entire head of the plunger covers the drain opening.

Now push down on it with force to create suction. Then, pull up the plunger to release the suction. Repeat this motion several times until the blockage is removed.

After repeating multiple times, check whether the blockage is cleared or not. Therefore, run water through the drain to flush away any remaining debris.

If the blockage still remains, move to the next method.

Method 2: Use Drain Snake or Drain Stick

After plunger use, you can use a drain snake or a drain stick when you see no visible difference. Both effectively clear clogs in a P-trap or S-trap caused by hair, food debris, and large object.

Remove the strainer or stopper to use the drain stick or drain snake. Then, insert the drain stick or snake into the drain and through the trap. You might have to turn the tool to locate the proper angle. To let the barbs, catch the substance, push the tip into the blockage as far as you can.

Now remove the drain stick or snake to extract any substance it catches. After that, run water through the drain to remove loose debris and reattach the strainer or stopper.

Method 3: Pour Hot Water and Vinegar Mixture

Another basic solution to fix a washing machine backing up into the sink is a hot water and vinegar solution. If you have no plunger, drain stick, or snake in your home, you can try this as a temporary solution.

Mix equal parts of hot water and vinegar and pour them into the sink. These can help break down any buildup or blockages, oil, grease, debris, soap scum, and mold in the drain. Let the solution sit for about 30 minutes, then run hot water to see if the issue has been resolved.

Method 4: Use Drain Cleaner

You can use a drain cleaner if the above solutions fail to work. However, be careful when using drain cleaners, as they can be harsh and may cause damage to your plumbing system if used incorrectly. Always follow the manufacturer’s instructions when using a drain cleaner.

Method 5: Clean the Lint Filter

This method is not for cleaning your sink drain pipe but for washing matching. A clogged lint filter can cause water to back up into the sink. You can clean the lint filter of your washing machine to see will resolve or not.

Precautions to Take When Fixing the Issue:

  • Before attempting to fix the issue, turn off the power to the washing machine to avoid any electrical hazards.
  • Wear gloves and safety goggles to protect yourself from debris or harmful chemicals.
  • If you use a drain cleaner, follow the instructions carefully and avoid overuse. Also, be cautious, as these products can be harmful if they come into contact with your skin or eyes.

Professional Solutions to Fix Washing Machine Backing up into Sink:

In the previous section, you acknowledge a few basic methods that can help. In that case, they fail to solve the issue; it would be best to seek professional help from a licensed plumber.

Here are some professional solutions that a plumber may recommend:

  • Plumbing inspection: A plumber may conduct a plumbing inspection to identify any issues with your plumbing system. They may use a video camera to inspect the drain pipe and identify any blockages or other problems causing the backup.
  • Hydro jetting: Hydro jetting is a process that uses high-pressure water to clear blockages in the drain pipe. This method effectively removes stubborn blockages and buildup that cannot be cleared with a plunger or drain cleaner.
  • Pipe replacement: If the plumbing system is damaged or old, a plumber may recommend replacing the drain pipe or other parts. This may be necessary if the existing pipes need to be bigger or correctly configured.
  • Washing machine repair: A malfunctioning washing machine can cause water to overflow into the sink. A professional washing machine repair technician can diagnose and fix any issues with your device, such as a malfunctioning pump or clogged drain hose.

The Cost of Fixing Washing Machine Backing up into Sink

The cost of fixing the washing machine backing up into the sink depends on several factors, such as the type of solution used, the severity of the issue, and whether you choose to DIY or hire a professional. Here are some factors that can affect the cost of fixing this issue:

1. Cost of DIY Solutions

If you choose to try DIY solutions like using a plunger, drain snake, or hot water and vinegar solution, the cost will be relatively low. You may only need to purchase essential plumbing tools or materials, costing around $10-$50.

However, remember that DIY solutions may not always work, and you may need to call a professional, which can increase the overall cost.

2. Cost of Professional Solutions

Hiring a professional plumber to fix the issue can cost more. Still, it may be necessary if the problem is severe or DIY solutions are failed. The cost of professional solutions can vary depending on the plumber’s experience, location, and the type of solution needed.

For example, hydro jetting or pipe replacement can cost anywhere from $300-$1000, while washing machine repair can cost around $100-$400.

3. Factors Affecting the Cost

Several factors can affect the cost of fixing the washing machine backing up into the sink, such as the severity of the issue, the type of solution needed, and the location of the problem. For example, the cost will be low if the issue is caused by a simple clog that can be easily fixed with a plunger or drain snake.

Moreover, the cost can be higher if the issue is caused by a more severe problem like a damaged or improperly installed pipe.


How to Prevent Washing Machine Backing up into Sink

  • Clean your washing machine and kitchen sink drain regularly and inspect the drain hose for clogs or damage.
  • Ensure that the p-trap is at the correct height and the drain hose is correctly inserted into the p- trap.
  • Install a lint trap on your washing machine hose to capture lint and other debris that could clog your pipes.
  • Avoid overloading your washing machine, which can cause it to back into the sink. Follow the manufacturer’s instructions for the appropriate load size.
  • Instead of doing one large load, run several smaller loads to prevent your washing machine from overloading.
  • Avoid washing bulky items like comforters and towels in the washing machine: Bulky items can cause strain on the washing machine and plumbing system, leading to potential backups. Consider washing these items at a laundromat or using a professional cleaning service.
  • Pouring grease down the drain can cause it to clog, leading to a backup. Instead, dispose of grease in the trash.
  • Please do not dispose of any solid items, such as food waste or grease, down the sink as they can clog the drain pipe.
  • Regularly run hot water through your washing machine and sink drain to break down mold, debris, oil, soap, or other buildups.

Follow the manufacturer’s instructions when using detergents and fabric softeners to prevent excessive buildup in the drain pipes.

Frequently Asked Questions

Can a clogged sink cause a washing machine to back up?

Answer: A clogged sink can cause a washing machine to back up. When both the sink and washing machine drain into the same pipe, a clog in the sink drain can prevent water from draining properly from the washing machine.

How often should I clean my washing machine drain?

Answer: It is recommended to clean your washing machine drain at least once a month to prevent any buildup of debris or residue that can cause blockages or backups.


To warp up, a washing machine backing up into sink is indeed annoying, but it’s not insurmountable. By understanding the causes of the problem and taking preventive measures, you can avoid this issue from happening.

And if it does happen, you now have the knowledge to fix it yourself or seek professional help. Remember, prevention is key, so make sure to regularly maintain your washing machine and avoid pouring harmful substances down your sink.

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