Fix a running toilet
Start by lifting the tank lid. A toilet that keeps running or refills on its own often has a problem with the flapper, chain or fill valve. Checking those parts takes just a few minutes, and replacements are inexpensive. Tackling it now can save a lot of wasted water.
How a toilet tank works
There isn't much in a toilet tank. A fill valve lets water in, a float tells it when to stop, and a rubber flapper at the bottom holds the water until you flush. When a toilet keeps running, one of those three isn't doing its job, and a few quick checks with the lid off will tell you which.
What's usually wrong
Rubber gets stiff and warped with age. Water seeps past it into the bowl, the tank level drops, and the fill valve turns on to top it up. That's the refill you hear every so often.
With no slack, the chain holds the flapper open a crack. With too much, it can get caught under the flapper.
Water rises until it spills into the overflow tube, so the fill valve never gets the signal to stop.
If it keeps hissing with a good flapper and the water at the right level, the valve itself isn't closing.
| What you notice | Most likely | Fix |
|---|---|---|
| Refills by itself every so often | Flapper leaking | Replace the flapper. |
| Water runs into the overflow tube nonstop | Water level too high | Lower the float. |
| Constant hiss, level looks right | Fill valve worn | Replace the fill valve. |
| Runs until you jiggle the handle | Chain too long or caught | Shorten the chain to about half an inch of slack. |
| Weak flush, then runs | Chain too loose or low water | Adjust the chain and float. |
Stop the running
- Test with food coloringPut 5 to 10 drops of food coloring in the tank and leave it for 15 minutes without flushing. If color shows up in the bowl, water is getting past the flapper, and you can skip to step 4.
- Check the chainWith the flapper closed, the chain should have about half an inch of slack. Move the clip a link or two if it's too tight or too loose, then flush to test.
- Look at the water levelIf water is running into the overflow tube, the float is set too high. Turn the adjustment screw on top of the fill valve, or squeeze the clip and slide the float down, until the water sits about an inch below the top of the tube.
- Replace the flapperTurn off the valve behind the toilet and flush to empty the tank. Unhook the old flapper from the two pegs on the sides and snap the new one on. If the old one feels soft, warped or slimy, that was the problem.
- If it still hisses, replace the fill valveIf the tank keeps filling with a good flapper, the fill valve is worn. A universal replacement kit costs about $12 to $20, and the instructions on the box are clear.
If it starts running again
Watch the tank right after a flush. If water keeps pouring into the overflow tube, look at the float and fill valve. If the level drops slowly with no sound, it's the flapper or the seat it sits on.
Run a finger around the rim the flapper closes against. If it's rough or pitted, even a new flapper won't seal. A flush valve repair kit adds a smooth new seat for about $15.
What a pro typically charges (a rough estimate; prices vary by area): A plumber typically charges $150–$300 to fix a running toilet, and most of that is the visit. The parts usually cost less than $25.
If it's a different toilet problem
Running toilet questions
Why does my toilet run for a few seconds every so often?
Water is slowly getting past the flapper, and the fill valve turns on to top the tank back up. A new flapper usually fixes it.
Can a running toilet raise my water bill?
It can. How much depends on how fast it's leaking and what you pay for water, but a toilet that runs steadily can show up clearly on the bill. The food coloring test in step 1 tells you whether yours is leaking.
Do I need a plumber to replace a fill valve?
Usually not. It's held on by one nut under the tank, and the universal kits come with good instructions.
Why is it still running after I replaced the flapper?
Check the chain first; new flappers often need it adjusted. If the flapper seals and the tank still refills, look at the water level and the fill valve.
Is it okay to leave it running until I can fix it?
It won't hurt anything, but it wastes water. Turning the valve behind the toilet off between flushes stops the waste until you can get the part.
Still stuck? Ask us
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