- Remove the tank lid. Carefully remove the tank lid and lay it flat on the floor to prevent it from falling over and breaking. Condensation on the underside of the tank lid may drip as you are removing the lid.
- Check the water level in the tank. If the water level is above the manufacturers indicated water line, make adjustments to correct the water level. If adjustments were made, reset the toilet by flushing it and allowing the tank to refill and stop on its own.
- Drop a dye tablet (available from your water provider) or several drops of food dye into the tank. Do NOT flush. Wait 15 minutes. If you have more than one toilet to test, repeat Steps 1 through 3 for each toilet while you wait.
- Check the water in the bowl for color. If the color appears in the bowl, there is a leak. Replacing the toilet’s flapper valve will likely stop the leak. To ensure proper flush performance, be sure the replacement flapper meets the toilet manufacturers specifications for your toilet model.
View more instructions on how to do a toilet dye test
How to fix common household leaks