Toilet Repair & Installation
Fix a running, leaking or clogged toilet or replace it.
Plumbing guide
Running Toilet Fix: Find the Leak and Stop the Water
A toilet that runs on its own is losing water through a part that no longer seals or shuts off. It is one of the cheapest plumbing repairs and one of the most expensive to ignore.
By the Urban Comfort Plumbing team ·
Why a running toilet matters
EPA warns that an old or worn flapper can make a toilet flush on its own or silently leak thousands of gallons a year, and it recommends replacing flappers at least every five years. A toilet that leaks into the bowl can waste hundreds of gallons a month with no noise at all. A toilet that runs audibly wastes more. You see it on the water bill, and a toilet that refills every few minutes also wears out the fill valve faster.
The cause is almost always inside the tank, where two systems work together. One lets water into the bowl when you flush and then seals. The other refills the tank and shuts off when it is full. A fault in either one makes the toilet run.
The dye test
EPA's WaterSense program uses the same test. Take off the tank lid and add a few drops of food coloring to the tank water. Do not flush. Wait about 15 minutes. If color appears in the bowl, water is leaking past the flapper, and the flapper or the seat it presses against needs attention. If no color appears and the toilet still runs, the problem is in the fill valve or the overflow.
The test is quick and also works for the silent leaks. A toilet can leak for months with no sound, and the dye test is the way to find out.
Replacing the flapper
The flapper is the rubber stopper at the bottom of the tank. Over time it hardens, warps or collects mineral film, and it stops sealing. Turn off the water at the shutoff valve under the tank, flush to empty the tank, and unhook the old flapper from the ears of the overflow tube and from the chain. Bring it to the store to match the type and size.
Install the new flapper, hook the chain with about a half inch of slack and turn the water back on. Wipe the flapper seat with a cloth to remove film before you install it. A flapper that does not seal because of a rough or pitted seat needs a seat repair, or the flush valve needs replacing.
Adjusting or replacing the fill valve
If water keeps flowing into the tank and down the overflow tube, the fill valve is not shutting off. Check the float, which is the ball or cup that rises with the water. If it is set too high, the water level reaches the overflow tube. Lower it, using the screw or the clip on the valve. A float that is cracked or waterlogged needs replacing.
If adjusting does not help, the valve itself may be worn or clogged with debris. Fill valves are inexpensive and easy to replace, and a modern one is quieter and faster. A hissing sound when the toilet is idle is another sign of a worn fill valve.
Chain, handle and other causes
A chain that is too short or too long, or one that hangs under the flapper, keeps it from sealing. A handle that sticks in the down position keeps the flapper open. Mineral buildup on the lever can hold it up. Adjust or clean these before you replace parts.
If the water level in the tank is above the top of the overflow tube, it will flow over and run constantly. That is a fill valve or float problem. If water is leaking at the base of the tank or from a supply line, that is a different leak, which needs a new gasket or line.
Replacing the whole flush set
If the flapper, the fill valve and the handle are all old, replacing them together is faster than doing them one at a time. Shut off the water and empty the tank, remove the old parts, set the new ones and adjust the water level and the chain. A flush valve kit includes the flapper and the seat, which fixes a worn seat at the same time.
Bring the model name from the inside of the tank or the bowl to the store. Most toilets use standard parts, but an older or specialty toilet may need a specific kit. If the tank is cracked or the bowl is chipped at the seat, replace the toilet instead.
Phantom flushing
A toilet that refills by itself every few minutes, with no one touching it, has a slow leak from the tank to the bowl. The water level drops a little, the fill valve opens to top it up, and the cycle repeats. It is the same flapper problem that the dye test finds, caught in the act. It is also the reason a quiet toilet can still run up the bill.
A note on St. Petersburg water
The City of St. Petersburg disinfects its water with chloramine. Chloramine can wear on some rubber and plastic parts faster than plain chlorine, which may be why flappers in some areas fail early. If yours keeps going bad, ask for a chlorine-resistant flapper or a replacement flush valve set. See toilet repair for the parts a plumber checks.
Parts to keep on hand
A flapper, a fill valve and a spare supply line cost little and cover most running-toilet problems. Keep a small adjustable wrench and a sponge handy for the tank. A few minutes with a new flapper is a better use of the afternoon than watching the meter run.
When to call a plumber
If you have replaced the flapper and the fill valve and the toilet still runs, the flush valve seat may be damaged, or the tank may be cracked. An old toilet may be near the end of its life. A plumber can replace the full internal set or the toilet.
Also call if the water bill is high and you have not found a source, since a running toilet may be one of several leaks. A meter test and leak detection check the rest of the house.
Common questions
Running toilet questions
It can waste hundreds of gallons a month, sometimes more. A dye test shows whether it is leaking.
EPA's WaterSense program recommends replacing flappers at least every five years, and sooner if the dye test shows a leak.
This is called phantom flushing. A slow leak from the tank to the bowl lowers the level until the fill valve turns on.
Often yes. A flapper and a fill valve are simple parts. Call a plumber if the problem continues.
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Toilet still running after a fix?
Call and describe what you replaced. The dispatcher will connect you with a local contractor.