The key is whether all the water goes out, or just down to the top of the drain opening. If it is being siphoned out for some reason, then it will sop draining when the water get below the trap opening. If it all drains out, especially if you have a jet hole at the bottom of the bowl, then the liklihood is that a crack has developed between the jet and the drain and the water is leaking out. E-mail me, and I will send my companys phone number and we can discuss it in real time and maybe come up with a solution. : Only one toilet on the second floor of my house in Mesa, Arizona daily empties the bowl/trap while the tank stays full. Of course then the sewer gas enters the house. No visible leaks, no other plumbing problems, no one is using the upstairs toilets, started without visible cause. Have had no solutions yet. Ideas short of an exorcism are welcome.