Toilet
A running toilet wastes water. A supply leak wets structure.
The two are easy to mix because both can move a meter. Only one of them stains a ceiling. A dye test in the tank is a cheap first check.
By ProShield Leak Detection Inc. · Updated
Dye the tank.
Food colouring in the tank should not appear in the bowl if the flapper is holding. If it does, you have a running toilet, not a mystery leak.
Look at the floor and the stop valve.
Wet at the supply, the coupling, or the wax ring is a different file from a silent refill.
The suite below still matters if the floor was wet.
A long-running toilet usually does not drip downstairs. A failed supply or wax ring can.
Questions people ask
Can a running toilet flood a suite?
It can overflow if the fill valve fails wide open. That is a shutoff event, not a dye-test event.
Does a running toilet need leak detection?
Not if dye and a dry floor explain it. Call if the floor or the ceiling below is wet.