Toilet keeps running or refills on its own

Question 1: What is the toilet doing?

• It refills by itself every so often when no one has used it: go to question 2
• It runs constantly and never shuts off: go to question 3

Question 2: Do a dye test: put a few drops of food coloring in the tank and wait 10 minutes without flushing. Does color show up in the bowl?

EPA says color in the bowl after 10 minutes means you have a leak from the tank into the bowl.

• Yes, the bowl water turned color: go to question 4
• No, the bowl stayed clear: Likely cause: a worn or stuck fill valve

Question 3: Lift the tank lid while it runs. Where is the water level?

The overflow tube is the open pipe standing in the middle of the tank, usually next to the flapper.

• Up at the top of the overflow tube, spilling into it: go to question 5
• Below the top of the overflow tube: go to question 2

Question 4: Look at the chain from the handle to the flapper. Is it pulled tight, tangled, or caught under the flapper?

• Yes, it is tight, tangled or caught: Likely cause: a chain that keeps the flapper from sealing
• No, it hangs loose with a little slack: go to question 6

Question 5: Gently lift the float (the ball or cup that rises with the water). Does the water stop?

• Yes, it stops when I lift it: Likely cause: the water level is set too high
• No, it keeps running: Likely cause: a worn or stuck fill valve

Question 6: Have you already put in a new flapper?

• No: Likely cause: a worn flapper
• Yes, and it still leaks: Likely cause: a worn flush valve seat or overflow tube