Why The Kitchen Sink Gurgles When The Washing Machine Drains: Complete Guide

Have you ever wondered why the kitchen sink gurgles when the washing machine drains its water!

Generally, your washing machine, bathroom sink, toilet, and even kitchen sink usually share the same waste pipe.

Once done washing, the washer will release loads and loads of water down the drain.

If there is any blockage along the drain, then a gargling sound will be produced by the sinks.

This happens when the water drains from the machine since there is not enough space for the large volume of water to escape.

So, what makes the kitchen sink gurgle now and then? Is it something you should be worried about? Can you fix it on your own?

In this guide, I will explore all the reasons as to why the kitchen since gurgles when washing machine drains.

I will also review some of the possible solutions to the problem.

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Why The Kitchens Sink Gurgles When The Washing Machine Drains: Reasons And Solutions

Why The Kitchen Sink Gurgles When The Washing Machine Drains

For your kitchen sink to gurgles when the washing machine drains, it simply means their drainage systems are connected to some point.

The gurgling sound from your sink is air from the drainage, which is escaping caused mainly by the pressure difference in the pipes.

If your vent functions normally, the air will not be trapped; instead, it will comfortably escape via the vent.

But if it is blocked, there will be an air build-up.

Therefore, once some significant volume of water is released to the drain, the air will find its way out, and the sink will be the only choice.

So, why does the kitchen sink gurgles when the washing machine drains?

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1)   Kitchen Vent Pipes Which Are Blocked.

If your washing machine is near the kitchen, they most likely share the drain with the kitchen sink.

The gurgling sound from your kitchen sink results from the vent being blocked.

So when the washing machine water is draining, the air in the vent will be pushed by the water, and because the vent is already blocked, the air will escape via the sink and thus the gurgling sound.

The sole purpose of the vent pipe is to allow the sewer gas to escape.

If it is blocked, then gurgling of the sink, bathtub, the toilet will take place.

Vent pipes run all the way to the roof of your house, where the sewer gas is vented out.

For you to establish if the vent system of your home is blocked, here are three signs to spot;

  1. Strong bad odors from the drain
  2. The gurgling of the sink, toilet, bathtub
  3. The speed at which water drains

2)   Poor Installation Of The Vent Pipes

Why The Kitchen Sink Gurgles When The Washing Machine Drains

Poor installation of the sink vent pipe is the first suspect when it comes to the gurgling of the sink.

If your sink is newly installed and it’s gurgling, then the pipes have not been installed as expected.

Routing of pipes correctly and proper joining of the vent pipe is vital.

If your sink drain uses the 1.5-inch drain pipe, then automatically, the vent pipe should be installed at a minimum of 3.5 feet away from the bottom of the trap.

This correct spacing allows the vent to pump sufficient air, thus creating the much-needed pressure difference in the plumbing system.

If the air is not well balanced inside the vent, then when the washer releases water with a lot of pressure, the vent will not regulate the air, so the gurgle will happen inside the sink.

In addition, you might also find that the plumber who installed your venting machine used a studor vent to help vent the drain from the washer.

Studor vents are a workaround of not running new vents through the wall.

3)   Damaged Or Leaking Vent Pipes

Like blocked vent pipes, a leaking vent can upset the pressure inside the drain system.

Low pressure will affect the correct flow of water and air inside the plumbing system.

When pressure is low, the air inside will automatically not get out as it should through the vent, but rather it will escape via the kitchen sink.

The air escaping through the sink creates a gurgling noise when draining the machine.

4)   Clogged Main Vent

Like the clogged kitchen sink vent, a clogged central vent can be much more problematic.

Since it’s the main vent, it usually regulates air pressure throughout the drain system, and if any blockage happens, the pressure will increase too.

Therefore, the air will eventually be trapped in the main vent pipe when the washer starts to drain its water via the drain connected to the sink drain.

Since the central vent is blocked, the air will escape via the sink drain, and that’s why your kitchen sink produces gurgling sounds.

 How To Fix A Kitchen Sink That Gurgles When The Washing Machine Drains

Identifying the specific sink which is gurgling in your house is the key to finding a solution to the problem.

A gurgle in your kitchen sink is directly related to issues in the drain or the sink pipes most of the time.

Below are some of the solutions you can employ at home before looking for any professional to come and assist you.

a)      Flush The Main Vent.

In many cases, the washing machine and the kitchen sink usually share a vent that then joins to the main vent, which extends to the roof of your house.

In cases where each has its vent connecting to the main one, then the reason for your sink to gurgle when the washer is emptying originates from the main vent.

You may find trash such as tree leaves, dust, or even broken tree branches having clogged the vent, thus altering the pressure inside the system.

Clear the debris then, using a pressurized pipe, blow water inside the vent to confirm it’s clear.

The water should not back up no matter the volume you have sprayed.

Always note this exercise is risky, therfore calling a professional would be ideal.

b)   Replace The Studor Vent

Studor vents, also known as the air admittance valve, are commonly used to replace sink vents.

It is not advised to use them to vent toilets since toilets require lots of air to keep the water and the waste to flow.

Lack of venting means there will be gurgling of toilets and sinks non-stop.

Studor vents are nowadays preferred as they significantly reduce the number of items needed for plumbing.

They are easy to install and reduce the number of roof repairs that might be required after roof vent repair.

Once a studor vent is clogged, you can easily replace it by yourself by just unscrewing and re-screwing back.

In addition, they are not as expensive. They range between USD 10 to USD 20 and can last a minimum of 20years.

c) Clear The Draining System

If you have confirmed that your p-trap, the main vent from the roof, and the studor (air admittance valve) are all ok, then it’s high time you tried a simple fix such as running hot water down the drain.

A minor clog down the drain may be the reason why your sink is gurgling. A clog means the drain cannot handle a lot of water from the washer.

In most cases, partial clog with time will always lead to complete blockage of your drainage.

Water draining more slowly than usual plus the gurgling of the sink are all indications of blockage of your main drain.

On the other hand, drain cleaners such as the Rid-X drain cleaner are really effective and environmentally friendly.

Green gobbler is also another enzyme-based cleaner that is quite effective.

Put some of the cleaners in your bathtub drainer, kitchen drain, and washer drain, and let it stay overnight.

Ensure they are not used at night too. The cleaner eats the soap remains and other organic things along the drain. This will make it easy to flush any other gunk.

You can use it often till the gurgling is clear, and after that, you can use it every three months.

It is safe and environment-friendly.

d)   Fix The P-Tap

P-trap is a U-shaped pipe beneath your sink.

It contains water which serves as a barrier to gases from the sewer to your home.

If a P-tap is not well installed, then a vacuum will be created. The created vacuum will pull all the water from the P-trap, so the sink’s gurgling will take place.

For instance, if the drainpipe is 1.5 inches long, the vent should be placed 3.5 feet from the lowest part of the p-trap.

e)     Thoroughly Wash Your Drain

In case the flushing of the drain does not work, it is now time to clean the drain.

Irrespective of how careful you are regarding food debris disposal, some will always go down the kitchen sink.

For those who use water from wells and boreholes, the mineral build-up can cause a problem on the drain.

With a basin placed under the P-trap, open it and clear the water inside it. Clean it and put it back.

Final Thoughts On Why the Kitchen Sink Gurgles When The Washing Machine Drains

Kitchen gurgling is always an indication something is not correct.

It is also not new for the kitchen sink and washing machine to share a drain.

Therefore if your kitchen sink gurgles when the washing machine drains, then something is blocking the flow of the water or something preventing the air from getting inside the drain, or both.

Therefore a gurgling sink should not be ignored since, in the end, it may cause a disaster to the whole drain.

A clog, improper installation, or even blockage are some of the reasons why the kitchen sink gurgle when the washing machine drains its water.

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