Toilet Keeps Running
A running toilet commonly means water is continuing to move from the tank into the bowl or overflow path. A worn flapper/flush-valve seal, incorrect chain position, fill-valve setting or failure, or a damaged flush-valve seat are common possibilities. Watching the tank water level and flapper behavior usually narrows the cause before any parts are replaced.
- —Worn or warped flapper not sealing the flush valve
- —Fill valve set too high — water spills into the overflow tube
- —Flush valve seat pitted or scaled
- —Lift chain too tight or too loose
Try This First
Safe, simple steps you can try yourself. If any step feels beyond your comfort level, skip it and continue below.
- 1
Take off the tank lid and watch the water level
If the water level is above the top of the overflow tube, water is draining down it continuously. Adjust the fill valve float down so the water stops about an inch below the overflow tube.
- 2
Check the flapper
Feel the flapper — if it's slimy, warped, or cracked, it's not sealing. Turn off the supply valve, note the flapper style, and take it to a hardware store for a replacement (a $5–10 part).
- 3
Check the chain
The chain should have a small amount of slack — not too tight (prevents the flapper from seating) and not too loose (can tangle under the flapper).
If the problem is resolved
If a new flapper and fill-valve adjustment stop the running, you've fixed it for under $15. Monitor it for a few days to confirm it doesn't return.
If the problem persists
If a new flapper doesn't hold, the flush valve seat (the surface the flapper seals against) may be pitted or corroded. That requires a flush valve replacement — continue below.
Stop and Call a Plumber If…
- A new flapper doesn't stop the running — the flush valve seat is likely corroded
- The tank is cracked or leaking
- Water is leaking from the base of the toilet
- The supply valve won't shut off the water
- ✓Inspecting the flush valve seat for pitting or scale
- ✓Replacing the flush valve assembly if the seat is corroded
- ✓Testing the fill valve for proper shut-off
- ✓Checking the supply valve and line for leaks
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Reviewed by Paul Hall, Owner & Licensed Plumber
The Classic Plumber · Knoxville, TN · License #4268. This guidance is general — an onsite inspection may be required for a confirmed diagnosis.