Why Is My Sink Gurgling? Causes, Fixes, and When It Is a Bigger Problem

A sink gurgles when air is being pushed or pulled through the water in its drain. That usually means a partial clog in the drain or a blocked vent pipe. Try a plunger and clean the P-trap first. If other drains gurgle or a toilet bubbles when you use the sink, the main drain line or a vent may be blocked, and you should call a plumber.

A gurgling sink is a sound you notice right away. It happens when the water drains, or even when you run another fixture, such as a washing machine or a toilet. It is not just noise. It is a sign that air and water are not moving the way they should in your drain system. Sometimes the fix is simple and takes ten minutes. Sometimes it points to something deeper. This guide helps you tell which one you have.

How a drain and a vent work

To understand the gurgle, it helps to know how the plumbing works. Every sink drains through a curved pipe called a P-trap. The trap holds a little water that blocks sewer gas from coming up. Behind the wall, the drain joins larger pipes that carry the water away.

Plumbing also has vent pipes. These run up through the roof. They let air into the pipes behind the water, so that water flows smoothly, and they let sewer gas out above your house. Think of pouring water out of a bottle. If the bottle has a wide opening, the water runs out easily. If the opening is tight, the water glugs. A vent keeps your drains from glugging.

When water has to push past a clog, or air cannot get in, it gets pulled through the trap, and that is the gurgling you hear.

The 6 most common causes of a gurgling sink

1. A partial clog in the sink drain

Hair, soap scum, grease, and food collect in the drain and trap. The water slows and pulls air along with it. This is the most common cause, and the easiest to fix. You may also see the sink drain slowly.

2. A dirty or clogged P-trap

The trap is the first place where gunk collects. A heavy buildup in it can make the sink gurgle even if the pipes behind it are clear.

3. A blocked vent pipe

Leaves, a bird's nest, a dead animal, snow, or ice can block a vent on the roof. Without air, the drain cannot flow right. If the gurgling began suddenly, in cold weather, or after a storm, a blocked vent is a good suspect.

4. A clog in the branch drain or main line

If the clog is deeper in the drain, more than one fixture may be affected. If the toilet gurgles when the sink drains, or the tub bubbles when the washer runs, the main line may be partly blocked. Tree roots, grease, and wipes are common culprits.

5. A failed air admittance valve

Some homes use an air admittance valve, or AAV, under the sink instead of a vent through the roof. These small one-way valves let air in. They can wear out over time and stop working, which causes gurgling.

6. An improperly vented drain

If the sink was added or moved in a remodel, the venting may not be right. A sink with a long drain run and no proper vent will gurgle every time it drains.

Quick test: how widespread is the problem?

Before you fix anything, run a test that tells you where the problem is.

1. Run the sink that gurgles. Note whether it also drains slowly.
2. Run other sinks in the house. Do they gurgle?
3. Flush a toilet. Does the sink or the tub gurgle or bubble?
4. Run the shower or the washing machine. Do any drains gurgle?

How to fix a gurgling sink

Step 1: Plunge the drain

A simple plunger can clear a minor clog.

1. Remove the stopper or strainer.
2. If it is a double sink, plug the other drain with a wet rag, so the pressure goes down the drain.
3. Put the plunger over the drain with enough water to cover the cup.
4. Push down and pull up with a steady rhythm for 15 to 20 seconds.
5. Run hot water to see if the drain flows. Repeat if needed.

Step 2: Clean the P-trap

If plunging does not work, take apart the trap.

1. Place a bucket under the trap.
2. Loosen the two slip nuts, one on each side of the trap. You can usually do this by hand, or with pliers.
3. Remove the trap and empty it. Clean out hair, gunk, and any objects.
4. Rinse it, check the washers, and put it back. Tighten the nuts by hand, then a quarter turn with pliers.
5. Run water and check for leaks.

If you see mold or the trap smells bad, scrub it with a small brush and dish soap.

Step 3: Snake the drain

If the clog is further down, use a drain snake, which is a flexible cable you feed into the drain. You can buy a hand-crank one at a hardware store. Feed the cable in until you hit resistance, then crank it to break up or hook the clog and pull it out. Flush with hot water.

Step 4: Use a safer cleaner

If you want to use a cleaner, an enzyme drain product is gentler on pipes than harsh chemicals. Baking soda and vinegar can help with light buildup, but they will not break up a serious clog. Avoid mixing different drain cleaners, and do not use chemical cleaners if the sink is full of standing water or if you plan to use a snake, because the liquid can splash you.

Step 5: Check the vent

You can check the vent from the roof, but this can be dangerous. If you are comfortable and it is safe, look at the vent pipe sticking up from the roof. Check for leaves, a nest, or ice. A garden hose can flush light debris. If you do not want to climb a ladder, or the roof is steep or wet, call a plumber.

Step 6: Look at the air admittance valve

If your sink has an AAV, which is a small plastic valve on a pipe in the cabinet or in the wall, it can fail. A new one is inexpensive, but you should have a plumber install it, since it has to be sized and placed to code.

When gurgling means a bigger problem

Some signs mean you should stop the DIY steps and call a plumber:

• More than one fixture gurgles or drains slowly.
• A toilet bubbles or its water level rises when you use the sink or the washer.
• Water or sewage backs up in a floor drain, tub, or shower.
• The gurgling comes with a sewer smell that does not go away. See a sewer smell in the house.
• You have snaked the drain and the trap, and it still gurgles.
• The gurgling began right after a plumbing repair or remodel.

A main line clog can lead to sewage backing into your home, which is a health hazard and a costly cleanup. A plumber can run a camera through the line to find the problem and clear it with a power auger or a hydro jet.

Related sink problems

A kitchen sink can gurgle for extra reasons.

• The dishwasher. The dishwasher drains through the same line as the sink in many homes. If the dishwasher is not draining right, see what to check when a dishwasher is not draining.
• The garbage disposal. A jammed or clogged disposal slows the drain. If it hums but does not grind, read why a garbage disposal hums but does not work.
• Hidden leaks. A drain that gurgles and also leaves a damp cabinet may be leaking. For help, see how to find hidden water leaks.
• A toilet that runs or bubbles. The toilet and the sink may share a drain. Look at a toilet that runs nonstop if that is also happening.

How to prevent a gurgling sink

• Use a drain strainer to catch hair and food.
• Do not pour grease or oil down the drain. Let it cool and put it in the trash.
• Flush the drain with hot water now and then.
• Run an enzyme cleaner every month or two if you have a slow drain.
• Do not flush wipes, even if the label says flushable.
• Have your main drain checked if you have old pipes or large trees close to your sewer line.

Bottom line

A gurgling sink is a sign that air and water are not flowing the right way. Most of the time a partial clog is the cause, and a plunger, a clean trap, or a small snake solves it. If several drains gurgle, a toilet bubbles, or the sound comes back, the problem is likely in the vent or main drain, and a plumber is the right call.