Virtually Design Your Own Sample Kitchen

When Flushing Toilet Sink Gurgles

Jump to Section

Do you have a gurgling sink when you flush your toilet? Or does your kitchen sink gurgle when your toilet is flushed? Does your bathroom smell like sewage? When your toilet sink gurgles, it can be pretty alarming. It's a sound that you don't normally hear in your home, so it can be confusing and frustrating. You may also face similar problems in your kitchen if you sink smells like sewer.

This problem can be caused by a number of different things, and it's important to get it fixed as soon as possible. Left unchecked, this issue can cause some serious damage to your plumbing system.

There are a number of things that can cause this problem, so let's look at the most common ones. Here are what may cause your sink to gurgle, the dangers it may cause, and ways to fix it.

Causes of a Gurgling Sink When Your Toilet is Flushed

You Have a Blocked Drain

The most common cause of a gurgling sink is a partially or completely blocked drain. When your toilet is flushed, the water has to go somewhere. 

When you have a partially blocked drain, your water will be draining slower than usual, and gurgling noises can be heard. If the blockage is more severe, your toilet water will start to back up and overflow. Therefore, don't let your drain stay blocked.

If you don't have anything about your partially blocked drain, then your toilet will become completely blocked. When water no longer drains down your sink or bathtub, your drain is completely blocked. Some of the causes of a blocked drain include dirt, hair, dead skin, soap residue, clogged wipes, and oils or grease.

A Blocked Sewer Line May Also Lead to a Gurgling Sink

A blocked sewer line may also lead to a gurgling sink and other plumbing problems. A clogged sewer line can cause the backup of water in your toilet bowl and other drain pipes, even if they aren't connected to the septic tank.

The main sewer line carries all your waste to the city sewer or septic tank. Your sewer line can become blocked by a number of things, including tree roots inside your sewer pipes, liquid fat that may also harden inside your pipes, and flushable wipes clogging your pipes.

Your sewer pipes may also deteriorate and begin to lose their structural integrity. Shifting the soil may also cause your pipes to break. Drain cleaners with sulfuric acid may also eat away at your pipes. And finally, a toy may get flushed, blocking your sewer pipe.

A Blocked Vent System

A properly working vent system is crucial to your plumbing system. Your drain and sewer pipe are connected to a vent pipe that exits through your roof. The vents allow fresh air into the sewer pipes so that the water can flow freely. If the vent pipe is blocked, the water won't be able to flow as freely and will begin to back up in your sink, toilet, or bathtub.

This will make your sink gurgle. And items that can block your vent pipe include small branches, tennis balls or baseballs, trash, leaves, birds, and small animals. Vent pipes help regulate the air pressure throughout your plumbing lines. They also help remove gas and odors with a plumbing system, allowing fresh air to circulate through your pipes.

If it's blocked, the sewer gases will start to escape through your drains, spreading throughout your home. Smelling sewer gases may cause problems such as headaches, nausea, shortness of breath, drowsiness, and heart palpitations. If you’re faced with such, try to reach a professional plumber because they know how to identify and remove a sewer gas smell in your house.

You May Also Have a Damaged or Blocked P Trap

Another potential cause of gurgling sounds when you flush the toilet is a damaged or blocked P trap. The P trap is the curved section of pipe that connects to the drain under your sink and forms a water seal to prevent sewer gas from entering your home.

If this trap becomes damaged, it can allow sewer gases to escape through the drains, which could cause a gurgling sound when you flush the toilet. Additionally, if the P trap becomes blocked with debris, it can prevent wastewater from draining out of your home properly, resulting in a gurgling sound as well.

If you smell sewage as you drain water down your sink, then it's time to replace your p trap. If the trap is behind your wall, call a professional before you start cutting into drywall.

How to Fix a Gurgling Toilet When it's Flushed

Use a Plunger

The first thing to do is to ensure that all sink drains are sealed tightly. After that, put your toilet plunger into good use. Press the plunger hard down and pull it up several times until you feel the blockage is removed and the air has gone through the sink drain.

After you've plunged the toilet, try flushing it and see if you can still hear a gurgling noise. If it does, repeat the entire process again.

Cleaning the Roof Main Vent Stack

This is a bit tricky, especially if you fear heights because you'll need to go up to your roof and find your main vent stack. It's common for the stack to get covered by leaves or other debris, and its screen will be dirty from the exposure.

You should clear both debris and screen. Take out a garden hose and begin to pour water down the vent. This will help you a lot because you can use it to clear out the vent pipe. If this doesn't work, it means there is a huge blockage that you can't eliminate using water.

To clear the blockage, make sure you know how to unclog a sink. You'll need to use a sewer auger, which you can easily rent. Be careful when using this tool because if you go too deep with it, you can damage your pipes and cause even bigger problems in the future. First, put the sewer auger into the vent opening.

Unwind the auger until you start to feel some resistance from the blockage. Once you feel it, you need to crank the handle and keep pulling the head of the auger out from time to time to get the debris out. When you no longer feel any resistance, you can spray some more water from the garden hose into the vent to clear it out.

Check the Air Admittance Valve

Air admittance valves typically work for at least twenty years without any issue, but they fail. If you have an air admittance valve installed on your trap, you should check to ensure it's working correctly. If it is leaking air or the door isn't sealing properly, you will need to replace the valve with a new one.

Check the Air Admittance Valve
Image credit:

This air admittance valve, also known as the cheater valve, is a gravity-operated device that helps release negative air pressure. When water and waste move down a drain, it creates negative air pressure in the pipe. This negative pressure lifts the cheater valve and lets air inside the pipe, allowing waste to drain away easily.

When the negative pressure drops, the cheater valve falls back into place. These valves are commonly found between the p trap and the drain line. They can deteriorate with time and needs replacement. All you have to do is to unscrew the old valve and replace it with the new one.

Cleaning the Sewer Lines

If the toilet gurgles when you flush, it could be a sign that your sewer lines are blocked. Sewer lines can get clogged with grease, soap scum, hair, and other debris. This can cause water to back up into your home, resulting in gurgling sounds.

Cleaning the Sewer Lines
Image credit:

The best way to clean your sewer lines is to hire a professional plumber to do the job. Plumbers have the tools and expertise to quickly and effectively clear your sewer lines.

If you have a septic tank, it's also important to have it regularly pumped and cleaned. A septic system that's not properly maintained can lead to problems with your plumbing, including gurgling noises. If you suspect your old toilet is the issue, then don’t hesitate to shop for some of the best flushing toilets in the market.

FAQs on Gurgling Sink When Toilet is Flushed

Why does the drain gurgle when flushing the toilet?

The drain gurgles because air is being forced through the water in the P-trap. This happens when the water in the bowl is flushed, and some of it goes down the drain, leaving a partial vacuum behind.

Why do my sink gurgle when flushing toilet?

There could be several reasons. If you have a septic tank, it might need to be pumped or cleaned. There could also be a blockage in the drain line. Another possibility is that the P-trap is not installed correctly, allowing air to enter the line.

Final Thought on Gurgling Sink When Toilet is Flushed

A gurgling sink when a toilet is flushed can be a serious headache, especially if you don't know the cause. But if you consider the above solutions, you should be able to fix the problem quickly and easily. If you're not comfortable executing any of these solutions, then it's always best to call a professional plumber. They will be able to pinpoint the exact cause of your gurgling sink and fix it in no time.




Kristina Perrin

Kristina Perrin

Kristina is an expert DIY home remodeler and mom to three. When she's not cooking or experimenting with new recipes, you can find her working on new home improvement projects or writing about her favorite kitchen appliances or DIY projects on Kitchen Infinity blog.

Related Articles
Don’t Miss Out On Great Black Friday Deals!

Download Free Chart Now!

Your email will be used only to confirm your request and to provide free kitchen information. By submitting your info on this form, you are agreeing to be contacted regarding your service request by means of email. This is no obligation form and doesn’t require you to purchase any service.