In the toilet tank I know that the overflow pipe is there for when the toilet tank is full. However my toilets overflow pipe in the tank doesn't go back into the toilet it goes to a pipe which runs along the waste pipe but what is that pipe attached to? where does it go. We have a major leak that no one can find and I am worried that pipe is the issue when it goes into the wall that it then isn't attached to anything. We know none of out live pipes are the issue and not our drains and waste pipe as water is clean.
The overflow pipe is for when the tank is full AND the normal fill-control system for the tank fails. If there is water entering the overflow pipe either due to a failed fill control setup or due to a leak in the connections at the bottom of the tank then that is a problem that should be fixed.
I would suggest adding some food coloring or similar dye into the tank. This should allow you to quickly determine if the water is coming from the tank or not.