Here’s Why Your Kitchen Sink Gurgles When Toilet Is Flushed

A well-functioning plumbing system doesn’t make weird sounds so you shouldn’t hear any gurgling in the pipes. Hearing a gurgling sound is actually an early sign of damage or blockage in the drainage system so don’t ignore it otherwise you may have some big problems in the near future. 

A gurgling sound coming from the kitchen sink when the toilet is flushing is not normal. It is a sign that there is an issue in the pipes, this could be a blockage, a damaged P-trap or a vent issue. Fortunately, you don’t need to be a plumber to solve the problem. 

Understanding Why the Sink Gurgles at End of Flush 

If you hear a gurgling sound from your kitchen sink when the toilet is flushing it is likely the result of a ventilation issue, debris in the pipes, or occasionally it may mean there is a problem with the plumbing hardware. Plumbing hardware issues are rare so it is more likely to be one of the first two issues.  

Why Does Your Sink Gurgle When Toilet Flushes? (4 Top Reasons)

A gurgling sink may seem harmless but it can actually indicate a problem in the drainage system. There are a few different reasons a sink may make a gurgling sound:

Clogged Pipes

A partial blockage in the pipes can mean the air goes through other drains in the house. So when the toilet is flushing, the air pressure is increasing and is being released through the kitchen sink or other outlets because there is something blocking or partially blocking the pipe.  

The P-Trap is Missing or Damaged

The P-trap is the U-shaped pipe under the sink, it prevents clogging and stops sewer gases from getting into your home. A damaged, broken or missing P-trap can cause your sink to make sounds. If this is the case, the gurgling sound is happening because the air is flowing uninterrupted through the drain. 

Clogged or Blocked Vents

The issue could be a clogged vent. The main vent stack is on the roof and could become clogged by dirt, debris, birds nests, leaves etc. Spraying water and using a drainage auger in the vent should help clear the problem. 

The Air Admittance Valve Needs Replacing 

Replacing the air admittance valve, also known as the cheater valve, can stop gurgling noises. These valves last a long time but are inexpensive and easy to change so it is always worth checking and replacing this in case. You can find the air admittance valve between the P-trap and the drain line. 

How to Fix a Gurgling Kitchen Sink 

Fixing the gurgling sound coming from a kitchen sink requires some troubleshooting. There are a few potential causes so these steps will work through the issues allowing you to find the damage or blockage and resolve the problem yourself. 

Things You Will Need:

  • Plunger
  • Drainage auger
  • Ladder
  • Flashlight
  • Garden hose

Step 1) Close the Sink Drain

The first thing to check is for blockages in the toilet. To do this, close the sink drain and protect the overflow tubes using duct tape. Closing the drain ensures you will only apply pressure to the pipes when attempting to clear blockages. 

Step 2) Use a Plunger to Remove Blockages

With the drain closed, use a plunger in the toilet to remove blockages in the waste pipe. After using the plunger, open the drain and flush the toilet to see if you still hear the gurgling noise. If the gurgling noise continues, repeat this process to make sure the issue is not caused by a blockage. If the plunging is alleviating the problem, continue doing this until the gurgling stops. 

Step 3) Inspect the P-traps 

If the plunger didn’t make a difference to the sound, move on to inspecting the P-traps. An easy way you can check the inside of a P-trap is by putting a small wire or thread into the drain. 

First, guide the wire into the kitchen sink and then pull it back out (imagine you are checking your car’s oil level). Remove the wire and check if the end of it is wet. If the P-trap is working well then 4 inches of the wire is going to be wet. If this is not the case, there may be an issue such as a crack that is letting the water escape. Do this with all the sinks in the house.

Step 4) Use an Auger to Clear the Pipes

You can use an auger to break up any clogs in the sink pipes. It is quite common for pipes to become clogged. An auger is the quickest and easiest way to remove dirt and debris as you simply feed it into the drain without needing to remove any pipes. 

Step 5) Check the Air Admittance Valve

An air admittance valve rarely needs any attention because it usually works for at least 20 years without issue. However, the gurgling noise could be the result of the valve being stuck, clogged, damaged or ill-fitting. Remove the valve from next to the P-trap and turn on the water briefly to see if the water drains properly. If it does, the issue is with the valve. 

Clean the valve and check it for damage. If there is damage then replace the valve. If you can’t see any damage then the issue could have been dirt or debris. Replace the valve and test the sink. 

Step 6) Check the Vent Pipe is Not Blocked

The next thing to check is the main vent pipe. If it is safe to do so, go up onto the roof with a flashlight, auger and hose and check the main vent opening. You can use the flashlight to look at the main vent pipe to see if you can see a blockage. If there is any visible debris, clean it away and then use a garden hose to see if the water runs through. If the water is not running well and is splashing back at you then there is a blockage. 

Step 7) Clear the Vent Pipe 

Depending on the location of the blockage, you may be able to remove the debris by hand but if not, use an auger to reach and remove the blockage. The water from the hose may even be enough to clear a clog. 

Step 8) Contact a Plumber 

If you have worked your way through these steps and the gurgling sound is continuing then it suggests a bigger problem that requires professional help. For example, there could be a blockage in the main sewer line and this is something a professional will need to deal with. 

FAQs: Gurgling Sound When Flushing Toilet

How vents get clogged? 

A clogged vent can be due to debris, leaves, bird nests, rodents and similar issues. It is relatively easy to unclog a vent but it requires going up onto the roof so you can get a professional to clear the vents for you. 

Why my basement toilet bubbles when upstairs toilet is flushed?

A toilet gurgling or bubbling indicates air pressure building up in the drainage system, this is due to a blockage or damage somewhere in the system. 

Are sink drains connected to toilet drains? 

Yes, all drainage pipes in the house connect. They all come together to connect to the main sewer pipe.  


A gurgling sink indicates a blockage or similar issue in your drainage system. It is best to troubleshoot the problem now before it develops. In many cases, you will be able to fix the issue yourself but if the problem continues after troubleshooting contact a professional to dig deeper into the system to find the cause of the gurgling sound

Recent Posts