1Look inside the tank
Lift the tank lid. Watch where the water is going: over the top of the overflow tube, or past the flapper at the bottom.
FREE REPAIR GUIDE
How to Fix a Running Toilet
Stop a toilet that keeps running: check the flapper, chain, fill valve and float. Most fixes cost under $15.
DIFFICULTYEasy
ESTIMATED TIME15–30 min
TOOLSNone (sponge, towel)
POTENTIAL SAVINGS$100–200Labour estimate · varies
Know what you’re replacing.
A toilet that keeps running or refills on its own can waste hundreds of gallons a day. The cause is almost always inside the tank: a worn flapper, a tangled chain, or a fill valve set too high. All three are easy fixes.
What you’ll need.
Universal toilet flapper (2" or 3")Check your flush valve size · ~$8
View on Amazon →
Universal fill valveIf the fill valve is worn · ~$12
View on Amazon →As an Amazon Associate, RepairAI may earn from qualifying purchases. Check that parts fit your exact model before buying.
A little preparation first.
- Take a photo inside the tank before you change anything.
- Find the shutoff valve behind the toilet.
One step at a time.
2Check the chain
The chain should have a little slack (about ½ inch). Too tight and the flapper can't seal; too long and it gets trapped under it.
3Lower the water level
If water spills into the overflow tube, turn the fill valve's adjustment screw or slide the float down so water stops about 1 inch below the tube.
4Replace the flapper
Turn off the water, flush to empty, unhook the old flapper from its pegs and clip in a new one. Reattach the chain.
5Test for leaks
Add a few drops of food coloring to the tank. If color shows up in the bowl within 15 minutes without flushing, the flapper still leaks.
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Troubleshooting
Still refills every few minutesThe flapper seat may be rough — clean it, or replace the flush valve.Fill valve hisses constantlyReplace the fill valve; they wear out after 5–10 years.Weak flush after the fixThe chain is too long or the water level is too low.
FAQ
How much water does it waste?A running toilet can waste 200+ gallons a day.Which flapper do I buy?Match the size (2" or 3") — check the drain opening or the toilet model.
General guidance only. Turn off power, water or gas before you work and follow the manufacturer’s instructions; if unsure, call a qualified professional.