Stop a running toilet
15 minutes · Easy · Estimated materials $0–$25
A running toilet usually comes down to the water level, flapper or fill valve.
Likely cause
The flapper is not sealing or the fill valve is sending water into the overflow tube.
First safe check
Remove the tank lid, set it safely on the floor, and watch where the water is going.
Tools and materials
Tools
- Towel
- Adjustable pliers
Materials
- Matching flapper, if worn
Step by step
- 1Set the tank lid flat on a towel.
- 2If water enters the overflow tube, lower the float until it stops below the tube.
- 3Press the flapper gently. If the sound stops, replace the flapper.
- 4Close the supply valve, flush, and fit a matching replacement.
- 5Reopen the valve slowly and watch one complete fill cycle.
Common mistakes
- Overtightening plastic parts
- Buying a flapper without matching its size
- Ignoring water at the toilet base
When to call a professional
Plumbing
Most of this is yours to do. Call someone licensed if any one of these is true — it's a judgement call, not a defeat.
- You cannot find or fully close a shut-off valve.
- Water appears in a ceiling, wall, or at the base of a fixture.
- More than one drain in the house is slow at the same time.
- The repair would mean soldering or opening a main line.
General guidance only. Codes and conditions vary. When in doubt, stop and use a licensed professional.