Question: How do I test if my toilet is leaking?
Answer: There are many ways to test if your toilet is leaking. One method is to open the toilet tank, put a coloring tablet or some food coloring in, and wait 15 to 20 minutes. Check the toilet bowl when you come back, not the tank. If there is a leak, the water in the toilet bowl will be colored.
If you don’t have any food coloring available, make sure your water rate is not above the tank's overflow tube. If so, your fill valve may be the issue. If you see water flowing down the toilet bowl when it is not being flushed, this is an indication of leakage. If your unused toilet creates a lot of noise (a running noise), you certainly have a leak. If you shake the flush handle and the sound stops, adjust the flapper valve and that should solve your problem.