Updated October 2026. Checked against This Old House, NDSU Extension and U.S. EPA guidance.
A toilet gurgles when air is pushed or pulled back through its water seal because wastewater cannot flow or vent freely. If only one toilet gurgles, it is usually a clog in that toilet or its drain; plunge it or use a closet auger. If several drains gurgle, the cause is more often the main line, a blocked roof vent, a full septic tank or a struggling drainfield. Gurgling with slow drains or sewage smell means the septic system should be checked soon.
What is making your toilet gurgle?
| What you notice | Likely cause | What to do |
|---|---|---|
| One toilet gurgles, other drains are fine | Partial clog in the toilet or its branch drain | Plunge with a flange plunger, then try a closet auger |
| Toilet gurgles when the shower, tub or washer drains | Clog in the shared drain line or a blocked vent | Snake the line; check the roof vent |
| Every drain is slow and toilets gurgle | Main line clog, full septic tank or clogged effluent filter | Stop heavy water use and call a septic company |
| Gurgling after heavy rain | Saturated drainfield or groundwater getting into the tank | Cut water use until the yard dries; have the system checked if it repeats |
| Gurgling plus sewage smell in the yard | Tank or drainfield problem | Call a septic company |
| Gurgling in winter | Frost or snow blocking the roof vent | Clear the vent; insulate or extend it |
Why a septic system makes toilets gurgle
This Old House explains that vents equalize the air pressure in the drain pipes so wastewater can flow freely. When a vent is blocked or a drain is partly clogged, flowing water creates a vacuum that pulls air through the nearest toilet trap, and you hear it gurgle. On a septic system, the same thing happens when wastewater backs up because the tank is full, a baffle or effluent filter is blocked, or the drainfield cannot take more water. NDSU Extension notes that the main vent stack on the house also vents gas from the septic tank, so a blocked vent affects the whole system.
How to fix a gurgling toilet
- Plunge. Use a flange (funnel-cup) plunger with enough water in the bowl to cover it. Plunge several times.
- Use a closet auger. If plunging fails, a closet auger reaches deeper without scratching the bowl the way a standard hand snake can.
- Check other drains. Run the tub and sink. If they also gurgle or drain slowly, the clog or problem is farther down the line.
- Check the roof vent. From a safe ladder position, look for leaves, nests, ice or snow. This Old House suggests hardware cloth held with a hose clamp if animals get in. If you cannot reach the roof safely, have a plumber do it.
- Have the septic tank checked. If the whole house is slow, ask when the tank was last pumped and whether the effluent filter needs cleaning.
Avoid pouring chemical drain openers into a toilet. The EPA recommends boiling water or a drain snake instead of chemical drain openers for septic systems, and boiling water can crack a toilet bowl. See septic-safe drain cleaners.
Several drains gurgling or slow?
That usually points to the main line, tank or drainfield. Talk to a local septic company about pumping or an inspection.
Calls are answered by a pay-per-call partner network that connects you with a local septic company. Calling is free; we may be paid for referrals.
Septic problems that cause gurgling
- Full tank. The EPA says most tanks need pumping every 3 to 5 years. See how to know if your septic tank is full.
- Clogged effluent filter. Many tanks have a filter at the outlet that slows the flow when it clogs. See how to clean a septic tank effluent filter.
- Blocked inlet baffle. Solids or roots at the tank inlet back up the main line.
- Saturated or failing drainfield. Wet, green or soggy ground over the drainfield is a warning sign. See how to fix a clogged drainfield.
- Tree roots in the line between the house and the tank.
Septifix is a tank treatment. It will not clear a clogged line, a blocked vent or a full tank, and Nebraska regulators say research shows little benefit from septic additives.
How to prevent toilet gurgling on a septic system
- Pump the tank on schedule, every 3 to 5 years for most homes (EPA).
- Flush only toilet paper and human waste. See septic-safe toilet paper and flushable wipes and septic systems.
- Spread laundry across the week so the tank and drainfield are not flooded at once.
- Keep grease out of drains.
- Clear the roof vent after storms, and insulate it in cold climates. See septic tank vent pipes.
Quick answers
Why does my toilet gurgle when the shower drains?
The shower and toilet share a drain and vent. A partial clog or blocked vent downstream pulls air through the toilet trap as the shower water passes.
Why does my toilet gurgle but flush fine?
Usually a partly blocked vent or the start of a clog. Fix it early, before it turns into a backup.
Is a gurgling toilet an emergency?
Not on its own. It is urgent if sewage backs up into a tub or floor drain, or if several drains are slow at once.
Will a gurgling toilet fix itself?
Rarely. A clog or full tank gets worse with use, so find the cause.
Sources
- This Old House, Toilet gurgling: causes and fixes
- North Dakota State University Extension, AE-892 Individual Home Sewage Treatment Systems
- U.S. EPA, How to care for your septic system
- University of Nebraska-Lincoln Water, Domestic sewage FAQs (citing Nebraska DEQ)