Why does my toilet flush on its own?

A toilet does not really flush on its own. It refills on its own. Those are different things, and the difference points straight at the cause.

Here is the cycle:

1. 1The flapper at the bottom of the tank should seal the drain hole between flushes.
2. 2If it does not seal perfectly, tank water creeps into the bowl.
3. 3The tank level slowly falls.
4. 4The fill valve senses the low level and runs for a few seconds.
5. 5The tank is full again, and everything goes quiet until the next drip-down.

Fluidmaster, a maker of toilet repair parts, describes how this sounds. It says you can hear a toilet refilling without being flushed, that it can happen every few minutes or every few hours, and that "Such a refill sound is usually alerting you that your toilet is losing water, either internally or externally."

Internal means water is draining into the bowl. External means water is getting outside the toilet, onto the floor or the tank exterior. Both are worth chasing down, and we cover both below.

### How much water can this waste?

More than you would guess, because the leak is silent. The EPA's WaterSense program says an old or worn flapper "can cause your toilet to flush on its own or silently leak thousands of gallons a year." EPA also reports that the average household's leaks can account for more than 9,300 gallons of water wasted every year, and that common leaks include worn toilet flappers.

So a toilet that refills by itself is a leak first and an annoyance second.

Do the dye test before you buy anything. It takes ten minutes, and it tells you whether the tank is leaking into the bowl.

EPA's instructions are short. Place a few drops of food coloring in the toilet tank. If any color shows up in the bowl after 10 minutes, you have a leak. EPA adds that you should flush immediately after the experiment to avoid staining the tank.

A few tips that make the test more reliable:

• Do not flush during the ten minutes. Even one flush mixes the dye.
• Put the dye in the tank, not the bowl.
• Use a dark color. Dye tablets made for this test work too.
• If the bowl water is already tinted by a cleaner, wipe or flush first and start clean.

### What if the dye stays in the tank?

Then the flapper is probably sealing. Your refill noise may come from somewhere else, such as the fill valve, the supply line, or a leak on the outside of the toilet. Skip ahead to the sections on the refill tube and outside leaks.

### A second check: the mark test

Fluidmaster has another way to catch a leak you cannot see. With the tank full, turn off the water to the toilet and mark the current water level inside the tank. Wait 10 to 15 minutes and note whether the water has dropped below your mark. If it drains down, Fluidmaster says to replace the flapper first, because it is the most common problem.

Turning the supply off is a nice trick. The fill valve cannot refill the tank, so a falling level proves water is leaking out through the flush valve.

You can also use your water meter. EPA says to check the meter before and after a two-hour period when no water is being used. If the meter changes at all, you probably have a leak somewhere. That does not tell you it is the toilet, but combine it with the dye test and you will know.

Work through these in order. They go from cheapest and easiest to most involved. Stop as soon as the dye test comes back clean.

### Is the flapper worn or dirty?

This is the top suspect. Fluidmaster says flappers are the leading cause of leaking or running toilets. The flapper is the rubber seal that closes the flush valve drain. Over time rubber hardens, warps, or picks up grit that keeps it from sealing flat.

EPA says the flapper should be checked periodically and replaced at least every five years to ensure a good seal and avoid leaks. Korky, another repair-part maker, says a flapper's life depends on outside factors such as the kind of water you use or whether you use chemical tablets to clean the tank. Its FAQ also says that if your toilet is running or flushing on its own, sometimes referred to as ghost flushing, it is time to replace your flapper.

Start with a cleaning. Fluidmaster's ghost flushing page tells you to wipe the flapper and the surface area of the flush valve clean, and to replace the flapper if that does not fix the running. To do it:

1. 1Turn off the water at the wall and flush to empty the tank.
2. 2Wipe the flapper with a cloth. Feel for stiffness, cracks, or a slimy coating.
3. 3Wipe the ring the flapper sits on, called the flush valve seat. Any grit there can hold the flapper open a hair.
4. 4Turn the water on and repeat the dye test.

If the leak persists, replace the flapper. Our page on how to replace a toilet flapper and fill valve walks through the swap, and how to pick the right toilet flapper explains sizing. Flappers come in 2 inch and 3 inch sizes according to Fluidmaster, so check before you buy.

### Are drop-in tank tablets chewing up the rubber?

Fluidmaster's flapper page says flappers wear out more often if you use drop-in bleach tablets. Its running-toilet page goes further. In capital letters it warns against in-tank drop-in bowl cleaners that contain bleach or chlorine, saying they can damage tank parts, may cause flooding and property damage, and void the warranty on Fluidmaster products.

If you have been dropping tablets in the tank and the toilet started ghost flushing afterward, that is a strong clue. Stop using them, replace the damaged flapper, and read the maker's label on any cleaner you use.

### Is the chain too tight, too loose, or tangled?

The chain links the handle arm to the flapper. If it is too short, it can pull the flapper open just a little. If it is too long, it can slip under the flapper and prop it open.

Fluidmaster's flapper instructions say to attach the chain clip to the tank lever directly above the flapper and leave 1/2 inch of slack in the chain. Check that nothing is snagged, then watch the flapper drop closed after a flush.

For a fuller rundown of a constantly running toilet, see how to fix a running toilet.

### Is the refill tube pushed too far into the overflow pipe?

This one surprises people. The small refill tube runs from the fill valve to the overflow pipe. It sends a little water to the bowl while the tank refills. Fluidmaster's ghost flushing page says to check this tube first. If it is inserted too far into the overflow pipe, pull it out and reattach it to the outside of the overflow pipe. That keeps the tube from entering the pipe and often stops an internal leak from the tank to the bowl.

Why does it matter? A tube that dips below the water level can act like a siphon straw and pull water out of the tank. Fluidmaster does not say why; this is our explanation of how it likely works. You do not need tools. Just clip the tube end to the top of the overflow pipe.

One caution. Toilet makers do not all agree on tube placement, because it depends on the design. Kohler's support page for its touchless flush toilets says to make sure the refill hose is inserted as far as possible into the flush valve, and to reposition the hose to minimize splashing. That advice is for a random flush on a touchless model, where the cause it lists is water from the flush valve splashing on the touchless module or the underside of the tank lid during refilling. If your toilet has a touchless or electronic flush, follow the maker's page for your model rather than the general advice above.

### Is the water level or fill valve height set wrong?

If the tank fills higher than it should, water can spill into the overflow pipe and run down the drain. That looks like a toilet that keeps topping itself off.

Fluidmaster says to look inside the tank and see whether the water level is rising so high that it drains into the overflow pipe. If so, follow the steps for cleaning the fill valve, and replace it if cleaning does not fix the problem.

Fill valve height matters too. Korky's instruction sheet for its 528 QuietFILL valve says to push the valve down until the fill valve water level is about 1/2 inch below the top of the flush valve overflow level. It notes that this puts the critical level mark on the cover 1 inch above the overflow level, which it labels a code requirement. Korky's FAQ also says its fill valves have an internal float, so you adjust the tank water level by turning off the supply and changing the height of the valve.

Different brands adjust differently, so follow the sheet that came with your valve. Our guide to adjusting a Fluidmaster fill valve covers that style.

### Is debris stuck in the fill valve?

Dirt can lodge in the valve and keep it from shutting off. Fluidmaster's steps for its valve are:

1. 1Turn off the water and flush the toilet.
2. 2Lift the float cup and hold the gray shaft in place.
3. 3Twist the cap and arm counterclockwise about 1/8 of a turn to unlock, then lift the cap away.
4. 4Hold an upside-down cup over the opening and turn the water on full force for 10 to 15 seconds.
5. 5Reassemble and turn the water back on.

Korky says its fill valves can be serviced by taking off the cap and pulling out the strainer. Fluidmaster says that if cleaning does not solve the problem, you replace the fill valve.

### Could the flush valve itself be the problem?

Yes, but it comes last. Fluidmaster says to replace the flush valve only after the flapper and cleaning fail. A cracked or pitted seat, or a valve that sits at the wrong height, can leak no matter how new the flapper is. If a fresh flapper still shows dye in the bowl, this is the next stop. Our page on leaks besides the flapper covers the other places a toilet can seep.

### What is the quick way to fix a phantom flush?

Use this order and stop when the dye test comes back clean.

1. 1Run the dye test, or the mark test with the water off.
2. 2Check the refill tube. Clip it to the outside of the overflow pipe, unless your maker says otherwise.
3. 3Clean the flapper and the seat with a cloth.
4. 4Check the chain for about 1/2 inch of slack and no snags.
5. 5Lower the water level if it spills into the overflow pipe.
6. 6Clean the fill valve.
7. 7Replace the flapper.
8. 8Replace the flush valve if a new flapper still leaks.
9. 9Stop using in-tank drop-in tablets.

If your toilet also fills slowly after it refills, our page on why a toilet fills so slowly picks up where this one leaves off, and why a toilet tank will not fill covers a tank that never gets full.

Random noise from a toilet is usually the same story: the toilet is telling you something is leaking or restricted. Fluidmaster's noise page sorts these sounds by what they mean.

### A refill sound with no flush

This is the ghost flush itself. It can cycle every few minutes or every few hours. Fluidmaster says it is alerting you that the toilet is losing water, internally if there is no water on the floor or outside the toilet, or externally if you see water outside. The fixes are the ones above: refill tube, clean and replace the flapper, and the flush valve as a last resort.

### A constant hiss or rush of air

Fluidmaster describes a constant noise that sounds like forced air moving through the toilet. It says the noise means water is constantly passing through the fill valve and into the tank. The fix is to clean debris out of the fill valve as described above. If your hiss is more of a whistle, see why a toilet fill valve whistles.

### A bang after the tank fills

A loud bang in the pipes after the fill valve shuts off is water hammer, according to Fluidmaster. It says water hammer can be caused by worn or damaged faucet washers, and that heavy mineral and rust buildup inside shutoff valves can also cause it. The same page describes a rapid banging or jackhammer sound during the fill.

Fluidmaster's whole-house reset steps involve shutting off the water at the main, opening all cold water faucets from top to bottom, flushing every toilet, waiting about 20 to 30 minutes, then turning the water back on and closing the faucets lowest first. If that does not work, it suggests reducing the flow at the shutoff valve. If that does not work either, it recommends calling a plumbing professional. Our page on pipes that bang or knock can help you sort out other pipe sounds.

### Noise from the wall valve

Fluidmaster also says a noise can mean the shutoff valve at the wall has an obstruction in the flow path. If you have a valve that is old, stiff, or crusty, replacing the toilet shut-off valve may be the cleanest fix.

### Water outside the toilet

If the refill sounds come with drips or damp spots, the leak is external. Fluidmaster lists these examples:

• Leaks from the bottom of a long-used fill valve, which it says should be removed along with the supply line and replaced.
• Leaks under the tank onto the bowl, which it says point to failed bolt seals, so the tank-to-bowl gasket and the toilet bolts with washers should be replaced.
• Supply lines older than 5 years, which it says to replace when reworking the fill valve connection.

Puddles at the base of the toilet are a different problem. See toilet leaking at the base. A tank that is wet only on the outside on a humid day may just be condensation, covered in why a toilet tank sweats.

Call a plumber if you have replaced the flapper, cleaned the fill valve, and checked the tube, and the dye still shows up in the bowl. That can mean a damaged flush valve seat or a valve set at the wrong height. Call if you see water on the floor, hear banging in the walls, or find that more than one toilet or fixture is acting up.

Our licensed and insured plumbers can find the cause and fix it, with upfront pricing and free estimates. If water is spilling onto the floor and you cannot stop it, turn off the toilet's supply valve and call. We offer 24/7 emergency service. For more on what we handle, see our residential plumbing services.