The short answer
A toilet that gurgles after you flush is pulling air through the water in a drain trap. In most Northern Virginia homes that comes down to one of two things: a partial clog in the line the toilet drains into, or a plumbing vent on the roof that’s blocked with leaves or a nest. One gurgle now and then is nothing. A gurgle on every flush, a bowl that sits low afterward, or a tub that bubbles when the toilet flushes is a drain giving you notice before it backs up.
What the gurgle actually is
Every drain has a trap, a bend that holds water to keep sewer gas out of the house. The toilet’s trap is built into the porcelain. When a few gallons rush down a pipe, air has to come in behind them, and that’s the job of the vent, the open pipe that goes up through your roof. When the pipe ahead of the water is partly blocked, or the vent is, the moving water pulls air from the closest place it can find: through the water sitting in a trap. That bubbling through the trap is the sound you hear.
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Where the gurgle is tells you where the problem is
Swipe to see all columns →
Swipe to see all columns →
| What you notice | What it usually means |
|---|---|
| The toilet gurgles once after its own flush, and drains fine | A partial clog in the toilet or just past it, often paper or a wipe hung up in the line |
| The toilet gurgles when the sink or shower next to it drains | The line they share is partly blocked past where they join, or the vent for that bathroom is |
| The tub or shower bubbles when you flush | The line the bathroom drains into is narrowing. Act on this one before it backs up |
| Toilets or a floor drain gurgle while the washer drains | The main line. A washer pumps out a lot of water in a hurry, and a narrowed main line can’t keep up |
| The bowl water drops low after the gurgle | The trap is being siphoned. A blocked or missing vent is the usual cause |
| A sewer smell comes with the gurgle | A trap pulled dry, or a vent not doing its job. What a sewer smell means |
A two-minute test
- Flush the toilet and watch the bowl. Water that drains, then settles lower than it normally sits, is being siphoned.
- Run the bathroom sink for a full minute and listen at the toilet. Then run the tub.
- Start the washer’s drain cycle, or fill and drain the kitchen sink, and listen at the lowest toilet and the basement floor drain.
- If only that one toilet gurgles, start with the toilet. If other drains join in, it’s the line or the vent.
If it’s just the toilet
A flange plunger, sealed over the hole with enough water to cover the cup, clears most partial clogs. If it still gurgles, a toilet auger reaches through the toilet’s built-in trap, where a toothbrush cap or a kid’s toy can sit for months, letting water by and making noise. How to unclog a toilet walks through both. If the toilet flushes weak as well as gurgling, why a toilet flushes slow covers the tank side.
If it’s the vent
The vent pipe sticks up through your roof, usually over a bathroom. In the fall it catches leaves, in spring birds and squirrels nest in it, and in a long hard freeze, frost can close it from the top. A vent problem looks different from a clog: the drains run at about normal speed but gurgle, the toilet bowl drops after a flush, and you may smell sewer gas inside. The plumbing vent pipe goes through the signs. Please don’t climb the roof with a hose. A wet roof is how people get hurt, and water sent down a vent over a clogged drain comes out at the lowest drain in the house.
If the gurgling sink is in a kitchen island or a basement bathroom, it may have no pipe to the roof at all, just a small one-way valve under the sink. Those stick. What an air admittance valve is.
If it’s the main line
Several drains gurgling at once, gurgling when the washer drains, or the lowest drains in the house going slow together all point at the main line to the street. Here that’s usually grease from the kitchen, wipes, or roots in old clay or tar paper pipe. Gurgling is the early warning, and a slow drain only gets slower. The backup comes later, and it tends to come on a holiday when the house is full. One drain or the main line covers how to tell, and if your house is from the 1950s or 1960s, Orangeburg pipe is worth a read.
If water comes up in a tub or a floor drain, stop running water and don’t flush. Every gallon you send ends up on the floor. Call (703) 997-9757. We run 24/7 emergency plumbing, and a sewer backup in the basement covers the first hour.
Houses on a septic tank
A house on septic gurgles when the tank is full or the drain field is soaked, and it’s often worse after a heavy rain. Most tanks get pumped every three to five years. If yours is past that, call whoever pumps it first. If it’s been pumped and the house still gurgles, the line between the house and the tank is the next place to look, and that’s a plumber’s job.
What not to do
- Don’t pour drain cleaner in a gurgling toilet. It sits in the bowl, and the next person to plunge splashes it. Is Drano bad for your pipes?
- Don’t keep flushing to see if it’s still happening when the water rises higher than usual.
- Don’t wait out a gurgle that’s new and doesn’t go away. A partial clog only gets fuller.
Want to see it on a real job? Gurgling drains, from one of our jobs.
When you’d rather we find it
A plumber can usually tell you in one visit where the gurgle starts. A plumbing diagnosis visit is $49, or $250 after hours. Clearing a toilet, tub or branch line is drain cleaning, $200 to $800. The main line to the street runs $550 to $1,650, and a camera down the line is $89 added to the visit, so you see the cause on the screen. When grease or roots keep coming back, hydro jetting clears the whole pipe wall. A sink clogged at the trap is $99 with our sink clearing offer, up to the P-trap. You get the price before we start.
Already holding a quote to dig up your sewer line? Send it to us for a free second opinion. You don’t owe us anything for looking.
Call (703) 997-9757, day or night, book a plumber online, or see every current deal on our offers page. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Questions people ask
Why does my toilet gurgle after I flush?
The water going down is pulling air through a drain trap, because the line ahead of it is partly blocked or the vent on the roof is. If only that toilet does it, start with a plunger. If other drains gurgle too, it’s the line or the vent.
Why does my toilet gurgle when the shower or sink drains?
They share a drain line, and it’s partly blocked past where they join, or the vent for that bathroom is blocked. The draining water pulls air through the toilet’s trap.
Is a gurgling toilet an emergency?
Not by itself. It’s a warning. It becomes urgent when water comes up in a tub or floor drain, or the toilet won’t go down. Then stop using water and call.
Can a clogged vent make a toilet gurgle?
Yes. Without air from the vent, draining water pulls air through the toilet’s trap instead. A low bowl after flushing and a sewer smell point at the vent.
Why does my toilet gurgle when the washing machine drains?
A washer pumps out a lot of water fast. If the main line is narrowed by grease, wipes or roots, it can’t take it, and air gets pushed and pulled through the toilet’s trap. That’s a main line problem.
How much does it cost to fix a gurgling toilet?
A plumbing diagnosis visit is $49. Clearing a toilet or branch line is $200 to $800, and clearing the main line runs $550 to $1,650. You get the price before any work starts.
