How to Stop a Toilet From Running: Easy Fixes

If you want to know how to stop a toilet from running, start by lifting the tank lid, because almost every cause sits inside that tank and can be fixed with a few inexpensive parts. A running toilet is usually a worn flapper, a chain that is the wrong length, or a fill valve set too high. This guide walks you through finding which one you have and fixing it yourself.

TL;DR

If water is spilling into the overflow tube, lower the float so the water stops about 1/2 inch below the top of the tube.
If the tank refills by itself every few minutes, the flapper is leaking. Clean the seat or replace the flapper.
Adjust the flapper chain so it has only 1 to 2 links (about 1/2 inch) of slack.
Confirm a silent leak with a dye test: food coloring in the tank, wait 10 minutes, check the bowl.
If the fill valve still won’t shut off after cleaning and adjusting, replace it, which is a manageable DIY job.

Why Your Toilet Keeps Running
Symptoms and Likely Causes
How to Fix a Running Toilet, Step by Step
What Not to Do
When to Call a Professional
How to Prevent It
FAQ

Why Your Toilet Keeps Running

A toilet tank has two jobs: hold water until you flush, then refill to a set level and stop. Water keeps running when one of two things happens. Either water is escaping the tank (through the flapper or over the overflow tube), or the fill valve never gets the signal to shut off.

Set the heavy lid on a towel and watch one full flush and refill. Where the water goes tells you which cause you have.

A Worn or Warped Flapper

The flapper is the rubber disc or cup at the bottom of the tank that lifts when you flush and drops to seal the drain opening. Korky, a toilet parts maker, calls it the most common cause of a leaking toilet. Over time the rubber hardens, warps, or gets coated in minerals, so it no longer seals.

Water trickles into the bowl, and the fill valve turns on to top off the tank. Tower-style flush valves use a rubber seal instead, which wears the same way and needs a model-specific part.

Phantom Flushing (The Tank Refills Every Few Minutes)

If the toilet refills for a few seconds every so often with nobody touching it, that is phantom or “ghost” flushing. Korky says this signals a leaking flapper that needs replacement.

Sometimes the culprit is grit or scale on the flush valve seat, the ring the flapper presses against. Cleaning it can stop the leak with no new parts.

A Chain That Is Too Short or Too Long

The chain connects the flush handle’s arm to the flapper. If it is too tight, it holds the flapper slightly open. If it has too much slack, the extra links can drop under the flapper and keep it from sealing.

Korky recommends 1 to 2 links of slack; Fluidmaster says about 1/2 inch.

Float or Fill Valve Set Too High

The fill valve is the tall assembly on one side of the tank. Its float (a sliding cup, or an older ball on an arm) rises with the water and shuts the valve off. Set too high, it lets water reach the overflow tube and pour down it nonstop.

Fluidmaster says water should stop about 1/2 inch below the top of the overflow tube. A float that sticks or rubs the tank wall causes the same overflow.

Overflow Tube and Refill Tube Problems

The overflow tube is the open pipe in the middle of the tank. A small refill tube from the fill valve clips onto it to refill the bowl. Fluidmaster says to clip it on, not push it down inside the pipe.

Less often, the overflow tube or flush valve is cracked. Korky notes that if the tank drains to the overflow tube or tank bottom with the supply off, the flush valve needs replacing.

A Worn-Out Fill Valve

Korky says fill valves typically last 5 to 7 years, less with sediment-heavy water. Signs include a valve that won’t shut off with the float lowered, slow or noisy filling, or hissing after the tank looks full.

If sediment is slowing water elsewhere too, see our guide to fixing low water pressure in a shower.

Symptoms and Likely Causes

Symptom	Likely cause	DIY or pro?
Water constantly spills into the overflow tube	Float or fill valve set too high	DIY: lower the float
Tank refills by itself every few minutes	Leaking flapper or dirty flush valve seat	DIY: clean seat or replace flapper
Toilet runs until you jiggle the handle	Chain too tight, tangled, or caught	DIY: adjust chain
Dye shows up in the bowl within 10 minutes	Flapper or tower seal not sealing	DIY: replace flapper or seal
Water keeps hissing in with the float lowered	Worn or clogged fill valve	DIY: clean or replace fill valve
Tank drains to the overflow tube or bottom with supply off	Cracked flush valve or overflow tube	DIY for experienced users; pro if unsure
Water on the floor around the tank or base	Leaking tank bolts, gasket, or supply line	Pro if the leak continues after tightening the supply connection

How to Fix a Running Toilet, Step by Step

Work through these in order. Most toilets are fixed by step 4 or 5.

Tools and parts: a sponge, a bucket, an old towel, a pencil or dry-erase marker, food coloring or dye tablets, adjustable pliers, a flathead screwdriver, a nonabrasive scrub pad, and (only if needed) a replacement flapper or fill valve.

Safety notes: Turn off the water at the shutoff valve behind the toilet (clockwise, by hand) before removing any part. Don’t force a stuck valve. Wipe up spills, and keep the porcelain lid where it can’t fall.

Step 1: Watch Where the Water Goes

Flush and watch the refill. If water pours into the overflow tube, go to step 3. If the tank shuts off and then turns back on later, do the dye test.

Step 2: Do a Dye Test

The EPA’s WaterSense program recommends this check. Put a few drops of food coloring or a dye tablet in the tank, don’t flush, and wait 10 minutes.

If colored water shows up in the bowl, water is leaking past the flapper or seal. Flush when you are done so the dye doesn’t stain the bowl.

For a second check, Korky suggests marking the tank’s water line, shutting off the supply, and waiting at least 25 minutes. A drop means a leaking part.

Step 3: Lower the Water Level

Most float-cup valves have an adjustment screw or rod on top. On Fluidmaster’s 400A, turning the screw counterclockwise lowers the level, and about eight turns moves the float roughly 1/2 inch. Other brands use a clip you squeeze and slide down.

Flush, let it refill, and adjust until water stops about 1/2 inch below the top of the overflow tube or at the tank’s water-line mark.

Step 4: Adjust the Chain

With the flapper closed, the chain should hang nearly straight with 1 to 2 links of slack. Move the hook to a different link to get there.

Flush and confirm the flapper rises fully, then drops squarely. Trim any long tail of extra chain.

Step 5: Clean the Flush Valve Seat

Shut off the water, flush while holding the handle, and sponge out the rest. Wipe the ring under the flapper with a nonabrasive pad.

If you feel cracks or chips on the ring, a new flapper won’t help.

Step 6: Replace the Flapper

With the tank drained, unhook the chain and slide the flapper’s ears off the pegs. Measure the drain opening or bring the old flapper to the store. Korky says pre-2000 toilets usually take a 2-inch flapper, while some newer ones use 3-inch.

If your chain has a small foam float, the City of Hendersonville, N.C., water department says to buy a flapper that includes one. Hook on the new flapper, set the chain, turn the water on, and repeat the dye test.

Step 7: Clean or Replace the Fill Valve

If water still hisses in with the float lowered, the valve is worn or clogged. Korky valves can be serviced, but Korky says other brands are better replaced entirely.

Mark the current water level with a pencil, shut off the water, flush, and sponge the tank dry.
Put a bucket or towel under the tank, then unscrew the supply line from the bottom of the valve.
Remove the plastic locknut under the tank and lift the old valve out.
Set the new valve’s height. Fluidmaster’s instructions call for the top of its valve to sit 3 inches above the overflow tube, which puts the critical-level mark 1 inch above it, as plumbing code requires.
Seat the valve with its washer, then hand-tighten the locknut from below while pressing down from inside. Don’t overtighten.
Make sure the float doesn’t touch the tank wall or other parts.
Clip the refill tube to the overflow tube so it arcs slightly and points down into it without being pushed inside.
Reconnect the supply line by hand, turn the water on slowly, and check for drips under the tank.
Set the water level about 1/2 inch below the top of the overflow tube.

Fluidmaster also recommends replacing the supply line if it is worn or more than 5 years old.

What Not to Do

Don’t just jiggle the handle and walk away.
Don’t overtighten plastic nuts with pliers. It can crack the nut or the tank.
Don’t use pipe tape or sealant on the supply connection unless the part’s instructions call for it. Korky says not to use either on its fill valves.
Don’t push the refill tube down inside the overflow tube.
Don’t drop chlorine or bleach tablets in the tank. Kohler warns that chlorine-based products can seriously damage tank parts and lead to leaks.
Don’t force a frozen shutoff valve. If it won’t turn, shut off water at the main and call a plumber.

When to Call a Professional

Call a licensed plumber if you notice any of these:

Water on the floor around the base or under the tank that returns after you wipe it up.
The shutoff valve behind the toilet won’t turn, won’t fully close, or drips from its stem.
A crack in the tank or bowl porcelain, even a hairline one.
The flush valve or overflow tube is cracked, since replacing it means removing the tank from the bowl.
You have replaced the flapper and fill valve and the toilet still runs or fails the dye test.

Renters should report a running toilet to the landlord before buying parts. The sources reviewed here don’t list repair prices, so ask for a written quote.

How to Prevent It

Run a dye test a couple of times a year. The EPA’s WaterSense program estimates that household leaks can waste close to 10,000 gallons of water a year in a typical home, and a silent toilet leak is one of the most common culprits.

Plan on replacing parts before they fail. The City of Hendersonville suggests a new flapper at least every five years, and Korky gives a range of five to ten. Korky puts fill valve life at 5 to 7 years.

Skip in-tank chlorine cleaners. Every few months, check that the chain isn’t tangled and the water stops below the overflow tube.

While you’re doing bathroom upkeep, see our tips on fixing a sink that drains slowly and on how to get rid of a drain smell.

FAQ

Why does my toilet run every few minutes on its own?

That is phantom flushing, and it almost always means the flapper is leaking slowly. Clean the flush valve seat first, and if that doesn’t stop it, replace the flapper.

How do I know if my toilet flapper is bad?

Do a dye test. Add food coloring to the tank, wait 10 minutes without flushing, and look for color in the bowl. A flapper that feels stiff, warped, slimy, or cracked when you pinch it is also due for replacement.

How high should the water be in a toilet tank?

Follow the water-line mark inside the tank if there is one. If not, Fluidmaster and Korky both say about 1/2 inch below the top of the overflow tube. Water above that will drain down the tube and keep the toilet running.

Can I fix a running toilet without turning off the water?

You can adjust the chain and float height with the water on. To clean the seat or replace the flapper or fill valve, shut off the supply and drain the tank first.

How long does a toilet fill valve last?

Korky says most fill valves last 5 to 7 years, depending on your water. A valve that won’t shut off, fills slowly, or hisses after the tank is full is due for replacement.

How to Stop a Toilet From Running