1. Remove the cover on the toilet tank and carefully set it aside so it can’t be accidentally knocked over and cracked. Remove any “in-tank” bowl cleaners that color the water and begin the test with clear water in the tank as well as in the bowl.
2. You’ll need some dye. Dye capsules or tablets, food coloring, instant coffee or powdered fruit drink mix all work fine. Now put enough dye in the tank water to give the water a deep color. Wait 30 minutes and make sure nobody uses the toilet.
3. In 30 minutes if you find any of the dyed water is now in the toilet bowl — your toilet is leaking. A properly operating toilet will store water in the tank indefinitely without any water running into the bowl.

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