You can fix this
Likely cause: the water level is set too high
If lifting the float stops the water, the fill valve works; the float is simply set high enough that water spills into the overflow tube. Lower it.
Why this happens
The float tells the fill valve when to shut off. If it is set too high, the tank fills past the top of the overflow tube and the water keeps draining into the bowl. Korky says to set the water level 1/2 inch below the overflow tube opening; Family Handyman gives 1/2 to 1 inch below the top of the overflow pipe.
How to fix it
- Find the adjustment on the float. Newer fill valves usually have a screw or clip on the float cup; older ball floats have a rod you can bend slightly down.
- Lower the float a little and flush.
- Watch the tank refill. The water should stop about 1/2 inch to 1 inch below the top of the overflow tube.
- Repeat until it stops at the right level and the running sound ends.
When to stop. If the float will not adjust low enough, the fill valve is likely worn. See the fill valve result.
If this does not fix it, tell the plumber
- The water spills into the overflow tube and stops when you lift the float.
- Whether adjusting the float changed anything.
Build the full list: what to tell the plumber.
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