A toilet that keeps running is usually caused by one of three small parts inside the tank: the flapper, the chain or the fill valve. Lift the tank lid and check each in turn, since a quick adjustment or a replacement rubber part is often all that is needed.
Look Inside the Tank First
Set the lid on a towel on the floor, away from where you will walk. Flush once and watch what moves. The tank holds water that drains through a large opening at the bottom, which a rubber flapper covers between flushes. A tall tube, the overflow, stands beside it, and the fill valve refills the tank.
- Water trickling over the top of the overflow tube points to a high water level or a fill valve problem.
- Water seeping past the flapper, with the bowl refilling every so often, points to a worn or misaligned flapper.
- A chain that is too tight or too loose keeps the flapper from seating.
A Sequence of Checks
- Tuck a few drops of food coloring in the tank and wait without flushing. Color in the bowl means the flapper leaks.
- Press down gently on the flapper. If the running stops, wipe the rim of the opening and the flapper edge with a cloth to remove slime.
- Check the chain. It should have only a little slack when the flapper is closed.
- Look at the fill valve. If the water level sits above the overflow tube mark, follow the maker’s instructions for lowering the float.
- If the flapper feels soft, warped or cracked, close the small shut-off valve near the floor, flush to empty the tank and swap in a matching flapper.
- Open the valve slowly, let the tank refill and watch for a minute.
Tools and Materials
| Item | Used for |
|---|---|
| Food coloring | Finding a flapper leak |
| Soft cloth | Wiping the seat and the flapper edge |
| Replacement flapper | Replacing a worn seal; match the type to your tank |
| Small pliers | Adjusting a clip or chain |
Fill valves and tank parts come in many styles, so check the maker’s guide for your toilet. If water leaks onto the floor, a shut-off valve will not close, or the problem relates to the main water supply, call a qualified plumber.
FAQ
Is a running toilet a big deal?
It can waste water over time, and it can be noisy. Many causes are simple, so a short check is worth the effort.
Why does the toilet run on its own now and then?
A slow flapper leak lets the tank drop a little, and the fill valve then tops it up. Cleaning or replacing the flapper commonly stops this.
The Short Version
Check the flapper, the chain and the fill valve in that order, using coloring to spot leaks. Replace worn rubber parts by the maker’s instructions, and call a qualified professional if water escapes or a valve will not move.