Fix Running Toilet

1 hr active work

$25 - $60

Beginner

Fix Running Toilet - DIY project preview

Fix a Running Toilet

A toilet that runs constantly or cycles on its own is usually a worn flapper or a fill valve sending water into the overflow tube. This guide helps you diagnose the cause before buying parts — most fixes take under an hour.

Step-by-Step Plan

Identify the symptom

Listen and observe to determine when the toilet runs: constantly (water always running), intermittently (cycles on/off every few minutes), or only after flushing. This helps diagnose the cause.

Tips

Constant running usually = fill valve issue (water going down overflow tube)
Intermittent cycling (phantom flush) usually = flapper leak
Running only after flush = flapper not seating or chain too tight

Perform the food coloring test

Remove tank lid. Add 5-10 drops of food coloring (or a dye tablet) to the tank water. Wait 10-15 minutes WITHOUT flushing. Check the bowl - if color appears, water is leaking past the flapper.

15m

Check tank water level

Look at the water level in the tank relative to the overflow tube. Water should be about 1 inch below the top of the overflow tube. If water is running into the overflow, the fill valve or float needs adjustment.

Adjust float if water level is high

If water level is too high: For ball float, bend the brass rod down slightly in the middle. For cup float (on fill valve), squeeze clip and slide cup down the shaft. Re-test water level.

10m

Replace flapper

If dye test showed a leak: Turn off water supply valve (behind toilet). Flush to empty tank. Unhook old flapper from overflow tube ears. Install new flapper, connecting chain to flush lever with slight slack.

15m

Replace fill valve

If float adjustment didn't help or valve is old/corroded: Turn off water and flush. Disconnect supply line. Remove locknut under tank (counter-clockwise). Remove old valve. Install new valve per instructions, adjusting height to match.

30m

Test the repair

Turn water back on. Let tank fill and observe. Flush several times. Verify toilet stops running when tank is full. Repeat dye test if you replaced the flapper to confirm seal.

10m