A running toilet is almost always fixed inside the tank, by replacing a worn flapper, adjusting the chain, lowering the float or replacing the fill valve. Lift the lid, watch where the water goes, and work through those four parts in order, since the cheapest and most common fix comes first.
Find out where the water is escaping
Take the tank lid off and set it somewhere soft. Two things can keep a toilet running. Either water leaks from the tank into the bowl past the flapper, or the tank overfills and spills down the overflow tube, the open pipe standing in the middle of the tank.
| What you see or hear | Likely cause |
|---|---|
| Water trickling into the top of the overflow tube | Float set too high, or a fill valve that won’t shut off |
| Tank refills by itself every so often with a short hiss | Flapper leaking into the bowl |
| Running stops when you jiggle the handle | Chain too long, tangled or catching |
| Constant hiss even with water below the overflow tube | Worn fill valve seal |
To confirm a silent flapper leak, use the dye test from the EPA WaterSense program. Put a few drops of food coloring in the tank and don’t flush. If color shows up in the bowl after 10 minutes, the flapper is leaking.
Replacing a worn toilet flapper
The flapper is the rubber seal at the bottom of the tank. Over time it warps, stiffens or collects mineral deposits, so it no longer seals. The EPA suggests replacing it at least every five years.
- Turn off the water at the shutoff valve behind the toilet and flush to empty the tank.
- Unhook the chain from the handle arm and slip the flapper’s ears off the pegs on the overflow tube.
- Wipe the valve seat, the ring the flapper sits on, with a sponge or scouring pad to remove grit.
- Fit the new flapper, hook the chain back on, turn the water on and test.
Flappers come in different sizes and styles. Take the old one, or a photo of it, to the hardware store, and check the toilet’s model number, usually stamped inside the tank.
Getting the flapper chain length right
A chain that’s too short holds the flapper slightly open. One that’s too long can get trapped under the flapper and stop it sealing. With the flapper closed, the chain should have a small amount of slack, enough that it hangs in a gentle curve without pulling. Move the clip one or two links at a time and flush between adjustments. Trim any long tail so it can’t drift under the seal.
Lowering the float so the tank stops overfilling
If water is pouring into the overflow tube, the float is letting the tank fill too high. On a modern fill valve, the float is a cup that slides up and down the valve body. Turn the adjustment screw or squeeze the clip to lower it. On older tanks with a ball on a long arm, turn the screw where the arm meets the valve, or bend the arm gently downward.
Aim for the water line marked inside the tank or on the fill valve. If there isn’t a mark, set the level clearly below the top of the overflow tube and check the manual for your model. Also make sure the small refill tube is clipped above the overflow tube rather than pushed down inside it.
When the fill valve itself needs replacing
If the float is set low and water still hisses in, the fill valve seal has likely worn out. Some valves have a replaceable cap seal, but swapping the whole valve is often easier. Universal fill valves fit most toilets and include instructions for height adjustment. Shut the water off, empty the tank, sponge out what’s left, unscrew the supply line and the nut under the tank, and install the new valve per its instructions.
Call a plumber if the shutoff valve won’t turn, the tank itself is cracked, or water leaks around the tank bolts after reassembly.
Frequently asked questions
Why does my toilet run every few minutes on its own?
That on-and-off refill, sometimes called phantom flushing, usually means water is slowly leaking from the tank into the bowl past the flapper. When the level drops far enough, the fill valve kicks on. Run the dye test, and if color reaches the bowl, clean the valve seat or replace the flapper.
Is a running toilet an emergency?
Usually not, but it can waste a lot of water and raise your bill until it is fixed. If you cannot repair it right away, turn the shutoff valve behind the toilet clockwise to stop the flow, and turn it back on only when you need to flush.
Do I need a plumber to fix a running toilet?
Most running toilets can be fixed without one, since flappers, chains, floats and fill valves are all designed for homeowner replacement. Call a plumber when the shutoff valve is stuck or leaking, the tank or bowl is cracked, or the leak is at the base or the supply line.
Why does my toilet keep running?
Usually because water is escaping inside the tank. A worn or warped flapper may be leaking into the bowl, the chain may be holding the flapper open, or the float may be set so high that water spills into the overflow tube. A fill valve that won't shut off is the other common cause.
How can you stop a running toilet in seconds?
Jiggle the handle first, since a chain caught under the flapper often keeps the water flowing. If that fails, lift the tank lid and press the flapper down so it seals, or raise the float to shut off the fill valve. These quick moves only buy time until you replace or adjust the part at fault.
What size toilet flapper do I need?
Most toilets take either a 2 inch or a 3 inch flapper, matched to the drain opening at the bottom of the tank. Fluidmaster says a flapper that measures about 3 inches across fits a 2 inch drain, while one about 4 inches across fits a 3 inch drain. Bringing the old flapper to the store also helps.
