Diagnose by Listening and Dye Testing

Use sound and food coloring to pinpoint whether the leak is at the flapper, fill valve, or overflow tube before making any repairs.

Steps

1. Remove the tank lid and listen closely: a hissing sound points to the fill valve; a quiet, steady trickle suggests a flapper leak
2. Add a few drops of food coloring to the tank water and wait 15-20 minutes without flushing
3. If colored water appears in the bowl, the flapper is leaking
4. If the tank water level is visibly above the overflow tube, the float is set too high
5. Use these findings to choose the correct repair

Tips

• The dye test is the most reliable way to confirm a flapper leak
• Flush promptly after the test to prevent food coloring from staining the porcelain
• Running this diagnostic first can save you from replacing parts that are not the actual problem