Toilet Clogged or Won't Flush: Stop the Overflow, Then Clear the Clog

A toilet that won't flush, or a bowl that rises toward the rim instead of draining, calls for one decision first: don't flush again. A second flush sends another tankful into a bowl that can't empty. Often the blockage is in the toilet's own trapway, the curved channel molded into the porcelain, and a flange plunger clears it. Korky, which makes toilet parts and plungers, calls plunging the best method for most backed-up toilets.

Below: stopping the overflow, telling a clog from a weak flush, plunging and augering, and knowing when the plumber takes over. If the toilet runs constantly instead, see toilet keeps running.

Stop the Overflow First

1. Don't flush again. American Standard and Korky both warn against it: each flush adds water the bowl can't hold.
2. Turn off the supply valve right away, as Korky and American Standard advise: the small oval handle on the wall or floor behind the toilet. Turn it clockwise until the tank stops filling. If it won't turn, don't force it; close the main water shutoff instead.
3. If water is still pouring from the tank, close the flapper. Lift the lid and press the flapper, the rubber flap at the bottom of the tank, down onto its seat. Per Korky, it lifts to let tank water into the bowl, then drops to seal the opening, so one stuck open keeps feeding the bowl. Tank water is supply water, not bowl water. Some toilets use a canister that closes the same opening.
4. Let the level drop. If the bowl is too full to plunge without splashing, Korky suggests waiting about 10 minutes, since most clogs aren't watertight. If it doesn't drop, bail some into a bucket. Lay towels around the base.

First, Is It a Clog or a Weak Flush?

A clog: the bowl rises after a flush and drains slowly or not at all; Korky says rising water usually means a clog. A weak flush: the bowl doesn't rise, but the flush is sluggish, leaves waste behind, or needs the handle held down. Look in the tank and at the rim.

A bucket of water tells them apart. A test from Kohler's pressure-assist toilet troubleshooting guide: with the bowl at its normal level, slowly pour in two to three gallons. If it drains away as you pour, the drain is open. If the level climbs, stop pouring: there's a blockage.

Most Likely Causes

1. Too much paper or waste in the trapway. Korky says a plunger clears a clog made of waste.
2. Something that doesn't break down. The EPA's do-not-flush list includes wipes, baby or "flushable," paper towels, diapers, cotton swabs, dental floss, and feminine hygiene products; American Standard adds facial tissues. Plunge first, then auger.
3. An object in the trap. Korky's advice: wear gloves and remove it by hand if you can reach it. If it's past reach, the toilet may have to come off the floor and go back on a new seal: a plumber's job.
4. A weak flush from the tank. Korky and Kohler list a slack chain that keeps the flapper from opening fully (Korky recommends one or two links of slack, Fluidmaster about half an inch), water below the tank's waterline mark, often from a float set too low, a refill tube not directed into the overflow tube, and the wrong size of flapper. Our running toilet guide covers the fixes.
5. Clogged rim holes. Tank water enters the bowl through small holes under the rim. Korky says mineral buildup can clog them until water drops straight down instead of swirling. Start with an in-bowl cleaner and a brush. For hard deposits, Kohler says to shut off the supply, flush, and ream each hole with a paper clip or a finishing nail; Korky advises gloves, eye protection, and a gentle hand, since porcelain chips easily.
6. A blockage past the toilet, or a blocked vent. Kohler lists a bowl that fills fast but drains slowly, sounds from other drains during a flush, and bubbles from the trapway as signs of a clogged waste stack or vent pipe.

What You Can Fix Yourself

Plunge with a flange plunger. Korky says a flat sink plunger can't seal in a curved toilet bowl; a flange plunger seals inside the outlet. Insert it at about a 45-degree angle so the head fills with water, center it over the outlet, and tilt it upright to seal. Push and pull in slow pulses so nothing splashes; Korky notes that the real power is in the pull. After several plunges, check; if the level drops only slowly, plunge again. Before turning the supply back on, pour in a bucket of water, as Korky suggests. If it drains normally, turn the water on and flush once.

Add dish soap and hot water once the level has dropped, so nothing splashes. American Standard suggests a generous amount of liquid dish soap, then a pot of hot water, not boiling. Wait about 10 minutes, then plunge again.

Use a closet auger. Kohler recommends a toilet auger (a closet auger, or toilet snake) to free a clog from the trapway; its cable runs through a guide tube with a bowl guard. RIDGID's instructions for its K-6P toilet auger: pull the crank up to draw the cable into the tube, set the tube's end in the drain opening, and turn the handle clockwise while pushing the cable forward. Keep the tube in the drain throughout, because RIDGID warns that the cable can damage the porcelain. If the cable sticks, stop turning and back it out. Keep turning clockwise as you retract it, and leave the tube in until the cable is fully back. Wear safety glasses and leather work gloves.

Skip chemical drain cleaners. Drano says not to use its clog removers in toilets, because the trap's shape keeps them from reaching the clog. It recommends only an enzyme build-up remover for a slow toilet, and says that won't open a full clog.

When It's the Main Line, Not the Toilet

Seattle Public Utilities describes one privately owned sewer pipe carrying a home's wastewater from sinks, drains, and toilets to the public sewer, so a blockage there shows up at more than one fixture. Watch for several drains slowing or backing up at once, water rising in a tub, shower, or basement floor drain when the toilet flushes, or other drains gurgling, which Minneapolis's sewer department lists as a sign of a clogged drain. If only one sink or tub is slow, see slow or clogged drain.

A plunger or a 3-foot auger can't reach that far. Stop using water and call a plumber or drain-cleaning service. They clear the line with a long cable; Seattle Public Utilities suggests asking whether the cable reaches the city's sewer main. Tree roots in a cracked pipe cause most backups, Minneapolis says; Seattle adds grease and anything flushed besides toilet paper. In both cities the homeowner owns that pipe, and if neighbors back up too, Minneapolis says to call the city. Seattle's first steps are to keep people away from the sewage and turn off power to eliminate electrical hazards; flip the breaker only from a dry floor with dry hands, never by wading in (see our burst pipe guide). Then clean up promptly, in rubber boots and gloves, and wash up thoroughly afterward, as Seattle advises.

When to Call a Plumber

• An object is stuck out of reach, or the clog comes right back after plunging and augering.
• Clogs keep recurring. American Standard notes that some older toilets have weaker flushing power.
• Water around the base, or a toilet that rocks. Korky points to the wax ring, the seal between the toilet and the floor drain, or the flange under it. The toilet has to come off the floor, and a cracked flange must be replaced.
• More than one fixture is backing up, or sewage comes up through a floor drain.
• The trapway is clear, but the flush is weak and drains gurgle. Kohler points to the vent, which exits at the top of the roof, per Minneapolis, and roof work is a pro's job.
• Drain cleaner is already in the bowl, or you smell sewer gas.

Our DIY vs. hire a pro guide covers how to hire one.

Prevent It

Flush only toilet paper, as the EPA asks, and keep a wastebasket in every bathroom for wipes, including "flushable" ones. If one toilet clogs often, try Kohler's test: shake a single-ply sheet in a quart jar of tap water for 10 seconds, about one flush. Kohler says the paper that dissolves or shreds the most flushes best. Clean the rim holes when the flush slows, and keep a flange plunger by every toilet.

Frequently Asked Questions

How do you unclog a toilet without a plunger?

American Standard's dish soap and hot (not boiling) water, left about 10 minutes, can loosen a clog, though it follows up with a plunger. A closet auger's cable reaches through the trap. Skip chemical drain cleaners, which Drano says don't belong in toilets.

Why is my toilet bowl filling up after I flush?

Something is blocking the trapway or the drain beyond it. Turn off the supply valve, close the flapper if the tank is still emptying, and plunge. If other drains gurgle or back up too, the blockage is farther down the line.

Can I pour drain cleaner in a toilet?

No. Drano says not to use its clog removers in toilets, where the trap's shape keeps them from reaching the clog, and never to plunge during or after using its gel. If some is already in the bowl, don't plunge or auger; call a plumber and tell them what was used.

Are flushable wipes safe to flush?

No. The EPA lists wipes, baby or flushable, among the things that can clog pipes and septic systems, and asks people to flush only toilet paper.

Will a clogged toilet unclog itself?

The level often drops on its own, since most clogs aren't watertight, Korky says, but the clog may remain. Test with a bucket of water before you flush, and plunge if the level climbs.

The Bottom Line

Don't flush again: shut the supply valve, press the flapper closed if the tank is still emptying, and let the level drop. Plunge with a flange plunger, then auger with the tube in the drain, and skip drain cleaner. A weak flush is the chain, the water level, the refill tube, or the rim holes. Several drains backing up, gurgling, water at the base, or a stuck object is the plumber's call.

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