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Washing Machine Backing Up Into Sink [4 Reasons & Solutions]

Recently, whenever you’d do laundry, your washing machine won’t drain.

Sometimes the water would overflow in your kitchen sink. And you’re not sure what’s happening.

This keeps you wondering why is your washing machine backing up into the sink?

Perhaps, there’s a clogged vent or p-trap that’s causing this issue. Or maybe your sink and washing machine share the same drain. To solve this, you need to clear the vent. You may also consider inspecting the hose and unbending it properly. Cleaning the water level valve can solve this, as well.

Are you still worried? Don’t be! Because this guide will solve your problems. Plus, there are some other great options for you!

Keep reading to find out!

Reasons Why Your Washing Machine Backing Up Into Sink

There can be a number of reasons why the washing machine is backing up. I have provided a few scenarios below. Consider going through them and you’ll surely be able to narrow it down.

Reason 1: Your Washing Machine And Kitchen Sink Share the Same Drain

In many households, kitchen apparatuses and washers usually drain through the same pipe. Food or grease constantly build up inside the pipe. Resulting in a slow down of the water flow. 

When it becomes bad enough or reaches a certain point, it may stop outright. It doesn’t only back up the kitchen equipment. Because, with that, it also backs up the washing machine.

Thus, water may back up in your kitchen sink when you are doing lots of laundry. Or the bathtub may fill with water. Either of these implies that the main drain line may be clogged.

Reason 2: Your Washing Machine Utilises Way Too Much Water for the Drain

The pipe which drains the washer is perhaps too small for the machine’s water capacity. Just imagine attempting to pour one gallon of liquid through a tiny funnel. That too, all at once. 

The liquid can not exit that funnel quick enough, resulting in an overflow.

It’s similar to what might happen if the washing machine discharges too much water in the drain. If that is the case, you certainly end up with one backed-up washer. That is comparable to that overflowing funnel. It often causes kitchen sink leakage.

Nonetheless, I hope it does not come to that. Sometimes, the older residences have those 1½-inch drain lines for washing machines. Modern washers are typically built for 2-inch drain lines. So, the issue is more prominent for the older models.

Reason 3: Problem with the Vent

You might hear a gurgling sound coming from the sink drain. It usually can be heard when your washing machine drains. It is the venting issue that is inducing the backup. 

Perhaps your washing machine or maybe the kitchen vent is operated inaccurately or it’s undersized. These can cause drainage issues. Similarly, it happens if that vent is plugged. 

Imagine a straw with some kind of liquid in it. If one side of that straw is plugged, surely the liquid won’t drain out. The plumbing system functions similarly. 

So there’s this gurgling sound coming from your kitchen sink. Be sure that the sink is being employed as a vent.

Reason 4: The P-trap Is Clogged

The p-trap is the section of pipe that’s behind the wall. And it comes in the U shape. It serves some purposes alright. Nevertheless, the concern is its potential in catching debris.

As water flows through the p-trap, lint, sand, and other stuff go at the bottom. That is in the U shape. It helps avoid clogs down the line. But when the p-trap becomes too full, it clogs. Thus making the washer back up.

This is probably the issue if you notice water on the wall. 

Solutions to Washing Machine Backing Up Into The Sink

At present, you have gone through all the possible reasons, you might’ve figured it out already. Now, according to your need, follow the solutions I have offered below!

Solution 1: Remove Obstructions

The washing machine and kitchen sink drain presumably connect to the 3-inch pipe. That is servicing any nearby toilet.

Your first job is to plunge into that toilet to discard the blockage. However, be very cautious before doing this. 

The plunging action might back water out of your dishwasher as well as the sink drain. To avoid this, you need to disconnect the sink P-trap. Then plug your wall drain using a rag. Finally, thrust on a cap so that the plug is watertight. 

You also might clear the drain using an auger. It’s much easier for an auger to get to the blockage. That is if you put it through a cleanout in the waste pipe.

Solution 2: Clear the Vents

What if cleaning the waste line did not solve your kitchen sink overflow problem?

You need to clear the vents.

However, inspect the vents first. The central vent stack stays on the roof. So you have to climb up there. Then you might find some debris blocking its opening. 

If not, you need to inspect the inside of that opening. It may show a blockage deeper down. Often you are not able to clear it with your hand. Then you have to spray water in that vent opening. 

Or maybe use an auger to clean it. 

When this vent is clear, it will offer a path for air to circulate. Then water should start flowing down the drain this time. And not into your kitchen sink.

Solution 3: Clean the Water Level Valve

This valve of the washing machine is identical to the water fill valve in the toilet.

When that valve is shabby, it will not sustain the water level appropriately. 

You will find the water level valve sitting behind the control panel. Inspect the tube directing to the valve carefully for any obstructions. Also, clean the valve with some vinegar and water solution in case of any corrosion.

You may consider cleaning the water inlet valve as well while you’re at it.

Solution 4: Inspect the Drain Hose

It may be that the drain hose is kinked. That is why you need to inspect the hose. That is liable for draining water from your washing machine. Irrespective of if the drain hose is too long or not.

Look if the hose bent in a certain way. If so, you have to unbend it. And then drain your washing machine.

Washing Machine Drainage Options

So do you find your washing machine drain backing up quite often? 

If yes, you might need to reconsider the washing machine drain options. 

If the current drainage option you have is not working properly, it will cause many problems. We provide you with some washing machine drainage options you might consider.

Use A Laundry Tub

A laundry tub might be one of the nicest drainage options for your washing machine. It needs a drain hose that is located 25 to 30 inches above the ground. Below 12 to 18 inches, your laundry tub will get to work.

When the washing machine drains the water, the water would move into the laundry tub. Thus, you can impede big particles from passing into the pipes. This way the clogs can be prevented.

Most of the premium washing manufacturers are seen to often suggest this kind of setup specification.

Install A Standpipe

Installing a standpipe for the washing machine is another great option. 

It’s an upright piece of pipe that includes an elbow at the bottom. The goal of the standpipe is to keep the machine’s water level below that of the drain. 

It will deter syphoning from the drain. A standpipe works as an outstanding drain hose backflow prevention for your washing machine.

Underground Pipe Connection

An underground pipe connection can be another amazing option for drainage work.  

This setup requires a standpipe. One part of that pipe would go underground. Usually, that pipe would be attached to your washing machine. It will be connected under the floor. 

Then the water can be thrust out of your house to the wastewater storage.


How does a master reset if my washing machine backs up?

To do a master reset, you need to first unplug the washer for 1 minute. Then, plug the accessory back in. You need to open the door 6 times within 12 seconds. It will notify your computer to conduct a reset. This can be a quick fix if your washing machine is compatible with the system.

Can a clogged P-trap cause your washing machine to back up into the kitchen sink?

Yes, a clogged p-trap can cause the backing up. As water streams through the p-trap, some lint, sand, and other stuff goes to the bottom. That is in the U shape. It helps avoid clogs down the line. But when the p-trap becomes too full, it clogs. Thus making the washer back up.

Why is a gurgling sound coming from my kitchen sink drain?

If a gurgling sound is coming from the sink drain, it is the venting issue.

Perhaps your washing machine or maybe the kitchen vent is operated inaccurately or it’s undersized. These can cause drainage issues. Similarly, it happens if that vent is plugged.


Hope I have cleared all your confusion about the washing machine backing up into the sink.

Make sure to identify the issues and solve them following the given instructions.

But, if you’re still confused, I suggest you go to a professional. A professional plumber can surely assist you in solving this issue.

That is all for today. Have an amazing day!