Toilet Won't Flush
If a gallon drains from the bowl, the tank is at fault.
By Jonathan West · reviewed 2026-10-21 ·how we research these
A toilet that won't flush has either a fault in the tank or a blockage in the bowl or drain. The bucket test tells you which. Pour about a gallon of water quickly into the bowl. If it drains, the problem is on the tank side. If the water level rises toward the rim, the blockage is in the toilet trap or drain, so stop pouring and do not flush again.
The sections below follow that split. The tank-side causes come first, then the clogs, then the weak flushes that have no clog at all, and last the cases where more than one drain in the house is affected. Each section names the part that has failed, what that part does during a flush, and the first thing to try.
The causes follow the sequence of a flush. The flapper or flush valve lifts, and tank water drops into the bowl fast enough to start the siphon. A symptom points back to the step that failed, so you can find the fault before you buy a part. Cost figures are typical United States (US) figures for orientation only. Do-it-yourself (DIY) fixes are listed for each cause, and the section on several slow drains marks where a licensed plumber is needed.
The Bucket Test: Clog or Tank?
The bucket test tells you whether the fault is in the tank or in the bowl and drain. Run it before you open the tank or buy a part. You need a bucket or pitcher holding about a gallon of water.
The gallon is a rule of thumb for this test. It is not a measured specification, so use roughly that amount. Pour it quickly into the bowl, all at once rather than in a trickle. Then watch where the water level goes.
If the water drains, the problem is on the tank side. Go to the handle and chain section first, then the low water section.
If the water level rises toward the rim, the blockage is in the toilet trap or drain. Stop pouring and do not flush again. Go to the clogs section.
Some blockages reach past the toilet. If the shower, tub or another drain gurgles or drains slowly, or water backs up in a lower fixture, the blockage is likely in the main sewer line or the vent. Read the section on several slow drains before you plunge anything.
Handle, Chain and Flapper (Tank Does Not Empty)
A flush starts when the flapper lifts, or when a flush valve opens, and lets tank water drop into the bowl fast enough to start the siphon. If the tank does not empty when you press the handle, the flapper is not lifting. Four faults stop that lift.
The symptom is the same for all four: the handle feels loose or has no resistance, and the tank stays full. Work through them in the order listed, starting with the nut at the handle.
Start by pressing the handle and feeling for resistance. If the handle moves with nothing behind it, tighten the nut that holds it to the tank. Then press again and see whether the tank empties.
If the handle lever is broken, the handle moves but the flapper does not lift. Replace the lever.
Inside the tank, look at the chain. It should run from the handle arm to the flapper. Hook it back on if it has come off. Set its length so that pressing the handle lifts the flapper, since a chain that is too long or too slack will not.
If the handle, lever and chain are all working and the tank still does not empty, the flapper is the next part to check. A flapper costs $5 to $15 in typical US figures. The step-by-step is on the flapper replacement page.
If the tank refills and water runs into the bowl with no flush at all, that is a different symptom. It is covered on the toilet keeps running page.
- The nut that holds the handle to the tank is loose.
- The handle lever is broken.
- The chain has come off the handle arm or the flapper.
- The chain is too long or has too much slack.
Low Water in the Tank
Too little water in the tank gives a weak flush that does not start the siphon. The water level is normally about an inch below the top of the overflow tube, so that is the mark to measure against.
Three faults leave the tank short of water. Check each one in turn.
Check the supply valve first. Turn it fully open, let the tank refill, and see where the water settles.
If the level sits low with the valve fully open, adjust the float so the water settles about an inch below the top of the overflow tube.
If the tank does not refill at all, the fill valve is the part to replace. A replacement fill valve costs $12 to $25 in typical US figures.
- The fill valve is not refilling the tank.
- The float is set low.
- The supply valve behind the toilet is partly closed.
Clogs: Plunger and Closet Auger
A bowl that rises on the bucket test has a clog in the toilet trap or the drain beyond it. Two tools clear that clog: a flange plunger and a closet auger.
Use a flange plunger, the kind with an extra rubber flap. The flange seals the toilet outlet better than a flat cup plunger does.
A closet auger, also called a toilet auger, reaches the trap without scratching the porcelain.
Do not pour chemical drain cleaner into a toilet and then plunge. The splashback is a chemical hazard, and the chemical can damage some fittings. Clear the clog mechanically.
A plunger or closet auger costs $10 to $40 in typical US figures. A plumber visit for a toilet clog commonly costs $110 to $250. The plumber cost page covers the ranges in more detail.
For a clog in a sink, shower or tub, use the general drain page.
Weak Flush With No Clog
A toilet can flush weakly with no clog in the trap. The rim jets, which are the holes under the rim, and the siphon jet, the hole at the bottom of the bowl, can clog with mineral deposits. A clogged jet gives a slow, weak flush.
Clean the jets with a small brush or a wire. A mirror helps you see the holes under the rim. Hard water makes this more likely.
Low water in the tank also gives a weak flush, so check the water level in the low water section before you clean the jets.
Federal law has set a maximum of 1.6 gallons per flush for toilets since the 1990s. The Environmental Protection Agency (EPA) WaterSense program labels toilets at 1.28 gallons per flush or less.
Low-flow toilets are more sensitive to a weak flush.
Dual-Flush and Pressure-Assist Toilets
A dual-flush toilet has two buttons that connect to the valve through a linkage or cable. That linkage or cable can disconnect. If one button does nothing, check the linkage or cable where it meets the valve.
Reconnect a disconnected linkage or cable, then press each button and watch the tank empty. A dual-flush fault that the linkage explains is a do-it-yourself reconnect.
A pressure-assist toilet uses a sealed air-pressure vessel inside the tank, and it is loud when it flushes. The vessel is sealed, so a pressure-assist toilet is typically left to a plumber or the manufacturer. Do not open the vessel yourself.
When Several Drains Are Slow
When the shower, tub or another drain gurgles or drains slowly while the toilet flushes, or water backs up in a lower fixture, the blockage is likely in the main sewer line or the vent.
Stop using water and call a licensed plumber. The price for a main line or vent job varies, so get a written quote from the plumber.
If the house is on a septic system, slow drains everywhere can mean the septic tank is full. Call a septic service for that.
Raw sewage is a health hazard. If water backs up into a lower fixture or several drains are slow at once, stop using water and call a licensed plumber.
When the Toilet Won't Flush: Symptoms, Causes and First Fixes
If the toilet still won't flush after one fix, run the bucket test again. A neighboring drain that gurgles tells you to call a plumber rather than try the next part.
| Symptom | Likely cause | First fix | DIY or plumber |
|---|---|---|---|
| Handle feels loose, tank stays full | Loose handle nut, broken lever, or chain off, too long or too slack | Tighten the nut, replace the lever, or reattach and set the chain | DIY |
| Tank water low, weak flush | Fill valve not refilling, float set low, or supply valve partly closed | Open the supply valve fully, then set the float about an inch below the overflow tube | DIY, with the fill valve costing $12 to $25 in typical US figures |
| Weak flush, bowl drains on bucket test | Clogged rim jets or siphon jet from mineral deposits | Clean the jets with a small brush or wire, using a mirror to see them | DIY |
| Bowl rises on bucket test | Clog in the toilet trap or drain | Flange plunger, then closet auger | DIY, or plumber visit commonly $110 to $250 |
| Button does nothing on a two-button toilet | Dual-flush linkage or cable disconnected | Reconnect the linkage or cable | DIY |
| Pressure-assist toilet that will not flush | Sealed air-pressure vessel in the tank | None at home | Plumber or manufacturer |
| Shower or tub gurgles during a flush, or water backs up in a lower fixture | Blockage in the main sewer line or vent | Stop using water | Licensed plumber |
| Slow drains everywhere on a septic system | Possibly a full septic tank | None at home | Septic service |
Common questions
How to force a toilet to flush?
Do not force the handle. Run the bucket test first, because the cause decides the fix. If the bowl rises on the test, a flange plunger or closet auger clears the clog. If the tank does not empty and the handle feels loose, reattach or set the chain and tighten the handle nut.
Why is my toilet not flushing all the waste away even though it's not clogged?
A clogged rim jet or siphon jet is one possible cause. Mineral deposits can block the holes under the rim and the hole at the bottom of the bowl, which gives a slow, weak flush with no clog. Clean them with a small brush or wire, and use a mirror to see the holes. Low water in the tank also gives a weak flush, so check the water level first.
Why is my toilet flushing water but the water won't go down?
If the water is not draining, the toilet trap or drain may be blocked. Run the bucket test to confirm it. If the level rises toward the rim, stop pouring and do not flush again. Clear the clog with a flange plunger or closet auger. If the shower or another drain gurgles during a flush, the blockage is likely in the main sewer line or the vent, and a licensed plumber is the next call.
Why isn't my toilet flushing when I press the button?
The handle or button may not be lifting the flapper. Check the handle nut, the handle lever, and the chain, in that order. A loose handle nut, a broken lever, a chain that has come off, or a chain that is too long or too slack each stops the flapper from lifting, and the tank stays full. On a two-button toilet, a disconnected linkage or cable does the same.
My toilet with two buttons isn't flushing. What can I do to fix it?
Check the linkage or cable between the buttons and the valve, since that linkage can disconnect. Reconnect it, then press each button and watch the tank. A pressure-assist toilet is different. Its air-pressure vessel is sealed, so that type is typically left to a plumber or the manufacturer.
What are the common reasons why a toilet won't flush?
The causes covered here are a loose handle nut, a broken handle lever, a chain that has come off or is set wrong, a fill valve that is not refilling, a float set low, a partly closed supply valve, clogged rim or siphon jets, a clog in the toilet trap or drain, a disconnected dual-flush linkage or cable, a sealed pressure-assist vessel, and a blockage in the main sewer line or vent. The bucket test separates the tank-side causes from the bowl and drain clogs.