Toilet Keeps Running: Fast Diagnosis Guide
A constantly running toilet usually wastes water because the tank is not sealing or refilling correctly.
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Before you startUse only the checks you can perform safely. Disconnect power before homeowner-serviceable cleaning or inspection. Stop when a repair involves gas, exposed wiring, high voltage, a roof, structural components, or anything outside your experience.
Common signs
- Water runs long after flushing
- Tank refills by itself
- Water bill rises unexpectedly
Most likely causes
1. Worn flapper
A warped flapper allows water to leak into the bowl.
2. Fill valve set too high
Water can spill into the overflow tube.
3. Chain problem
A chain that is too tight or tangled can hold the flapper open.
4. Mineral buildup
Deposits may prevent a clean seal.
Safe checks to try first
- Remove the tank lid and observe what happens after a flush.
- Make sure the water level stops below the overflow-tube opening.
- Check that the flapper chain has a little slack.
- Press gently on the flapper; if the running stops, replacement is likely needed.
When to call a professional
Call a plumber if the shutoff valve leaks, the tank is cracked, or replacement parts do not solve the problem.
Bottom line
Start with the simplest visible cause, change one thing at a time, and avoid repeated resets or disassembly when a safety device keeps tripping. A recurring problem usually deserves a proper diagnosis rather than a temporary workaround.