If your toilet keeps running, you are not alone. It is one of the most common plumbing problems in any house. Maybe you hear the tank refill on its own at 2 a.m. Maybe your water bill jumped and nothing else changed.
The good news is that most running toilets come down to a cheap part inside the tank. A few drops of food coloring will tell you which one. This guide walks you through that test, the three usual causes, what you can fix yourself in an afternoon and the signs that it is time to book a plumber.
How a Toilet Tank Works, in 30 Seconds
Lift the lid off the tank and you will see a few simple parts. When you push the handle, a chain lifts a rubber flap at the bottom of the tank called the flapper. Water rushes into the bowl. The flapper drops back down and seals the hole.
Then the fill valve, the tall part on one side, refills the tank. A float rides up with the water and shuts the valve off at the right level. In the middle stands the overflow tube, an open pipe that sends extra water into the bowl so the tank can never spill onto your floor.
A toilet that keeps running means water is escaping from the tank somewhere, and the fill valve keeps trying to top it back up. Your job is to find where it is escaping.
The one thing to check: the 15-minute food coloring test
1. Take the lid off the tank and set it on a folded towel. Lids are heavy and crack easily.
2. Put a few drops of food coloring in the tank water. Blue or green is easiest to see.
3. Do not flush. Wait 15 minutes.
4. Look in the bowl. If color shows up in the bowl, the flapper is leaking. If the bowl is still clear, the flapper is sealing and the problem is the water level or the fill valve.
5. Flush a couple of times when you are done so the dye does not stain the bowl.
Why Your Toilet Keeps Running: The Three Usual Suspects
1. A worn or warped flapper
Signs: the dye test puts color in the bowl. The tank refills for a few seconds every so often when nobody touched it. The running stops when you press down on the flapper with a stick.
Why it happens: the flapper is rubber. Over time minerals and chlorine in the water make it stiff, warped or slimy, so it no longer seals tight.
The fix: replace it. Turn the shutoff valve behind the toilet clockwise until it stops, then flush to empty the tank. Unhook the chain, pop the flapper's ears off the two pegs on the overflow tube and put the new one on. Take the old flapper to the hardware store so you buy the same size. Most are 2 inch and some newer toilets use 3 inch. While the tank is empty, wipe the ring the flapper sits on with a scrub pad. Mineral crust there can stop even a new flapper from sealing.
2. The fill valve is set too high
Signs: the dye test comes back clear. With the lid off you can see or hear water trickling into the top of the overflow tube. There may be a steady hiss.
Why it happens: the float is letting the water rise too high. The extra water spills down the overflow tube into the bowl, so the valve never gets to shut off.
The fix: lower the float. Most newer fill valves have a float that slides on the valve body, with a screw or clip on the side to adjust it. Older toilets have a ball on the end of an arm, with a screw where the arm meets the valve. Set the water to the line marked inside the tank. No line? Aim for about an inch below the top of the overflow tube. If you lower the float and the valve still will not shut off, the valve itself is worn out and needs replacing.
3. The chain is too short or too long
Signs: the running starts right after a flush. Jiggling the handle stops it.
Why it happens: a chain that is too tight holds the flapper open a crack, so it never seals. A chain that is too loose can get trapped under the flapper.
The fix: move the clip on the handle arm so the chain has a little slack, about half an inch, when the flapper is closed. Trim the extra chain so it cannot fall under the flapper. Check the handle too. A loose or sticky handle can hold the flapper up.
One more to check: the little refill tube
A thin tube runs from the fill valve to the overflow tube. It should be clipped so its end sits above the top of the overflow tube. If it has been pushed down inside the tube below the waterline, it can siphon water out of the tank and keep the fill valve cycling. Clip it back up.
This is not a small leak to put off. The EPA's WaterSense program says a running toilet can waste about 200 gallons of water a day. You can read its leak checking tips on the EPA Fix a Leak Week page.
Toilet Keeps Running After You Replaced the Flapper?
This happens a lot. Before you give up, run through this short list:
· Wrong size or wrong style. A 2 inch flapper on a 3 inch opening will never seal. Match the old one or check the toilet maker's part number, usually stamped inside the tank.
· Dirty seat. Scrub the ring the flapper sits on. A small nick or rough spot there will leak no matter how new the flapper is.
· Chain length. A new flapper often sits at a slightly different height, so the old chain setting may now be too tight.
· Water level. Run the dye test again. If the bowl stays clear, look at the water level and the fill valve next.
· Adjustable flapper set wrong. Some flappers have a dial that controls how long they stay open. Follow the setting on the package for your toilet.
What You Can Fix Yourself and When to Book a Plumber
Fine to do yourself
· Replacing the flapper
· Adjusting or trimming the chain
· Lowering the float
· Clipping the refill tube back in place
· Cleaning the flapper seat
· Replacing the fill valve, if you are comfortable following the package steps
Time to book a plumber
· A crack in the tank or bowl, even a hairline one. Porcelain cannot be patched reliably.
· Water on the floor at the base of the toilet, or a toilet that rocks. The seal under it may have failed and the floor can be getting wet.
· A shutoff valve that will not turn or drips when you turn it. Old valves can snap.
· The ring the flapper sits on is cracked or pitted. Fixing it means taking the tank off the bowl.
· You replaced the flapper and the fill valve and it still runs.
· Your bill is high but every toilet passes the dye test. The leak may be somewhere else in the house.
A quick way to check for a hidden leak: turn off every faucet and appliance that uses water, then look at your water meter. Many meters have a small dial or triangle that spins when water is moving. If it moves while everything is off, water is going somewhere. That is a job for a plumber. Our plumbing services page explains how booking works, and if water is actively spreading across a floor, start with our emergency plumber guide.
When you do call someone, ask them to look at the job in person and give you the price in writing before work starts. Ask for their license and proof of insurance too. Our guide to choosing a plumber in Columbus, Ohio has a good list of questions that work in any city.
Find Help Near You
Need more than a new flapper? These pages cover the jobs a running toilet can turn into, from a quick part swap to a full bathroom update.
Toilet Keeps Running: Common Questions
Why does my toilet run for a few seconds every so often when nobody used it?
That is called a phantom flush. Water is slowly leaking from the tank into the bowl, usually past a worn flapper. When the tank level drops far enough, the fill valve turns on for a few seconds to top it back up. Do the food coloring test. If color shows up in the bowl, replace the flapper.
Is a running toilet an emergency?
Usually not. It wastes water and money but it will not flood your home on its own, because the overflow tube sends extra water into the bowl. If you cannot fix it today, turn the shutoff valve behind the toilet clockwise to stop the water and turn it back on when you need to flush. Water on the floor is different. Shut the valve off and book a plumber.
Jiggling the handle stops it. Is that fine?
It works for the moment but it is a clue, not a fix. If jiggling the handle stops the running, the flapper is not dropping back into place on its own. The usual cause is a chain that is too short or tangled, or a handle that sticks. Adjust the chain so it has a little slack and check that the handle moves freely.
How long does a toilet flapper last?
There is no fixed number. The rubber breaks down over time and it wears faster with hard water, chlorinated city water and drop-in tank cleaning tablets. When a flapper feels stiff, warped or leaves a black smudge on your fingers, it is due. The part is inexpensive, so there is little reason to keep an old one.
Will a running toilet really raise my water bill?
Yes. A toilet that runs all day sends clean water straight down the drain around the clock, and many homeowners first notice it as a bill that jumped for no reason. If your bill went up and the dye test on every toilet comes back clean, have a plumber look for a leak somewhere else in the house.
Should I replace the whole toilet instead of fixing it?
Only if the porcelain is cracked or the toilet is so old that parts are hard to find. The flapper, chain, fill valve and handle are all standard replacement parts. A crack in the tank or bowl cannot be patched reliably, so that is when a new toilet makes sense. If you are updating the whole room, a bathroom remodel is a good time to do it.
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