Toilet Keeps Running? Stop It Tonight Without a Plumber
- Under half an hour
- 7 parts and tools
A toilet that runs and runs after you flush is wasting water every minute it goes, and the sound can drive you out of your mind at night. The good news is that a running toilet is almost always a small rubber part or a simple adjustment inside the tank, not a plumbing emergency. You can diagnose it in about five minutes and fix most causes in under half an hour, with no tools or with one pair of pliers at most. Nothing in this guide requires shutting off water to the house. The shutoff valve for the toilet is right behind the bowl, and you will only need it if you decide to replace a part.
What's probably wrong
Work through these causes in order, because they are listed from most likely to least likely.
A worn flapper is the number one cause. The flapper is the rubber disc or cup at the bottom of the tank that lifts when you flush and drops back down to seal the tank afterward. Rubber wears out in chlorinated water, and after a few years it warps, cracks, or gets a slimy coating that stops it sealing. When the seal leaks, water trickles from the tank into the bowl nonstop, and the fill valve keeps topping the tank up to compensate. That is the running sound you hear. If your toilet is more than three years old and has never had a new flapper, this is your prime suspect.
A chain problem is the next most likely cause. The chain connects the flush handle arm to the flapper. If the chain is too short, it holds the flapper slightly open all the time, and water leaks through constantly. If the chain is too long, it can slip under the flapper and hold it open, or tangle and stop the flapper dropping cleanly. Either way, the symptom is the same endless running.
A fill valve set too high is the third common cause. The fill valve is the tall valve on the left side of the tank, connected to the water supply line. It has a float that rises with the water and shuts the valve off at a set level. If that level is set above the top of the overflow tube, water pours down the overflow tube forever, and the valve never shuts off. You can spot this one instantly, because you will see water flowing into the overflow tube, which is the open topped pipe in the middle of the tank.
A damaged overflow tube or flush valve seat is less common. The overflow tube can crack, which lets water leak into it below the intended level. The flush valve seat, which is the rim the flapper seals against, can get pitted or coated with mineral scale, so even a new flapper cannot seal against it. This cause is worth knowing about because it explains the toilet that keeps running after a new flapper did not fix it.
A faulty fill valve is the least likely cause for a toilet that was fine last week. Fill valves do wear out, and when they do they may hiss, take forever to refill, or fail to shut off at all. If you have ruled out the flapper, the chain, and the water level, the fill valve itself is what is left.
Fix it tonight
Start by taking the lid off the tank and setting it somewhere safe, on a towel on the floor. Porcelain lids chip easily and they are awkward to hold, so put it down before you do anything else. Then flush once and watch what happens inside the tank. This one observation tells you most of what you need to know.
First, check the water level. After the tank refills, the water should sit about one inch below the top of the overflow tube. If water is flowing into the overflow tube, the fill valve is set too high. Find the adjustment on your fill valve. On most modern valves it is a screw on top of the valve or a clip on the float rod. Turn the screw counterclockwise, or slide the clip down, to lower the shutoff level. Flush and let it refill, then check again. Repeat until the water stops about one inch below the overflow tube top. This single adjustment fixes a surprising number of running toilets.
Second, check the flapper. Look at the rubber disc at the bottom of the tank. Press it down gently with your fingers to make sure it is seated flat. If the running stops when you press it, the flapper is either worn or not seating properly. Run your finger around its underside. If it feels warped, rough, or leaves black smears on your fingers, it is done. Lift the flapper off its pegs and take it with you to the store for matching, or measure its diameter. Most are two inches or three inches. A universal flapper fits most toilets and costs a few dollars. Clip the new one onto the same pegs, connect the chain, and flush to test.
Third, check the chain. With the flapper seated, the chain should have about half an inch of slack. That is roughly the width of your little finger. If it is tight as a guitar string, it is holding the flapper open. Lengthen it by moving the hook to a different link. If it is so long that it pools under the flapper or catches on things, shorten it the same way. Flush a few times and watch the flapper drop cleanly and seal flat each time. A chain that is too long can also be trimmed with pliers, but rehooking is easier and reversible.
Fourth, do the dye test if the running persists and you cannot see the problem. Put a few drops of food coloring, or a dark drink mix, into the tank water. Do not flush. Wait 15 minutes. If color shows up in the bowl without a flush, water is leaking from the tank into the bowl, which confirms a flapper or flush valve seat problem. If no color appears, the leak is the overflow tube or the fill valve, and the water level adjustment or a fill valve replacement is the fix.
Fifth, if the fill valve itself is the problem, you can replace it tonight if you are comfortable with one water connection. Turn off the shutoff valve behind the toilet by turning it clockwise. Flush to empty the tank, and sponge out what is left. Disconnect the water supply line from the bottom of the old fill valve with pliers, unscrew the lock nut, and lift the old valve out. Set the new valve to the same height as the old one, drop it in, tighten the nut, reconnect the supply line, and turn the water back on. Adjust the water level to one inch below the overflow tube. If any step here feels uncertain, leave it for the morning and call a pro. A toilet that runs overnight wastes water, but it is not an emergency, and a calm morning repair beats a midnight flood.
Parts and tools
When to call a pro
Call a plumber if a new flapper and a correct water level do not stop the running, because that points to a damaged flush valve seat or a cracked overflow tube, and both require removing the tank. Call a pro if the shutoff valve behind the toilet is seized, corroded, or drips when you turn it, because forcing it can break the valve and cause a real leak. Call a pro if you see water on the floor around the base of the toilet, which is a different problem from a running tank and may mean a failed wax ring. Call a pro if the tank itself is cracked. A running toilet is not an emergency, so if it is late and the fix is not working, you can turn off the shutoff valve behind the toilet overnight and sleep in silence, then call in the morning.
What a pro typically costs
These are broad typical ranges, not quotes. Your area will change the number. A plumber visit to fix a running toilet typically costs 120 dollars to 300 dollars, including a replacement flapper or fill valve. Replacing a flush valve, which requires removing the tank, typically costs 200 dollars to 450 dollars in total. Replacing a seized shutoff valve typically costs 150 dollars to 350 dollars. If the plumber finds a cracked tank or a damaged bowl, replacement of the whole toilet typically costs 400 dollars to 900 dollars installed, depending on the model you choose. For a simple running toilet, expect the low end of these ranges, because the fix is usually one small part and under an hour of work.
FAQ
How much water does a running toilet actually waste?
A toilet that runs constantly can waste a large amount of water in a day, easily tens of gallons and sometimes hundreds, depending on how fast the leak is. That is why it is worth fixing tonight even though it is not an emergency. Your water bill will show the difference next month.
I replaced the flapper and it still runs. What now?
Recheck the water level first, because a level set above the overflow tube causes running no matter how good the flapper is. If the level is correct, do the dye test. Color in the bowl without flushing means the flush valve seat is pitted or scaled, and that is a job for a plumber, because the tank has to come off.
Can I turn the water off overnight and deal with it tomorrow?
Yes. Turn the shutoff valve behind the toilet clockwise until it stops. The toilet will not refill, and the running will stop. You can still flush once with a bucket of water poured quickly into the bowl if you need to. Turn the valve back on in the morning when you are ready to fix it or when the plumber arrives.
How long should a flapper last?
In most homes, three to five years. Chlorine in the water and cleaning tablets that sit in the tank shorten its life. If you use in tank cleaning tablets, expect to replace the flapper more often, and consider switching to a cleaner that does not sit in the tank water.