How to tell if your toilet is leaking, and what to do
Toilet leaks are the most common household leaks. Many are silent, so the only way to know is to test.
The food coloring test
- Put ten drops of food coloring in the toilet tank.
- Put the lid back on and don't flush.
- Wait twenty minutes.
- Look in the bowl. If you see colored water, the toilet is leaking.
Tell your landlord or maintenance. The usual cause is the flapper, the rubber part at the bottom of the tank. Flappers often last about five years and leak once they stop sealing.
If a toilet starts to overflow
Close the valve on the wall behind the toilet by turning the round handle clockwise. Or take the lid off the tank and lift the float. Then clear the clog with a plunger, or call maintenance.
Keep it from clogging
Flush only waste and toilet paper. Keep a trash can in the bathroom for everything else, including wipes.
Rent your home? Get the free move-in safety checklist. Own or manage rentals? SaferResident gives every tenant a 20 minute course on this, built around your building.
Sources
- How to catch a running toilet, Portland Water Bureau, City of Portland, Oregon
- How to Prevent Interior Water Damage from Plumbing and Appliances, Insurance Institute for Business and Home Safety (IBHS)
Updated October 1, 2026. General safety information. It doesn't replace your building's safety systems, local codes or your lease. In an emergency, call 911.