Why is My Toilet Bowl Empty?
It is strange to look into a toilet bowl and find it totally dry. Where did the water go? A couple of possibilities come to mind. Imagine when you go to bed the toilet bowl looks normal with water in the bottom of it. You wake up to use the bathroom and now it is dry.
One possibility is that you may have a crack in the bottom of the bowl. These are very hard to see. The way the toilet trap is laid out is that it runs under the bowl. So if the bowl is cracked, the water would drip into the trap and you would never have any evidence of a leak on the floor around the toilet. Some people would say that if this was the case, the toilet would be running. That’s not true as there is no water demand from the tank until the toilet is flushed.
Another possibility is that you have a clogged vent. The vent runs to the exterior out of the roof. In order for the drain to work correctly there must be an air supply, and the vent provides this. It is simply a pipe that is connected to the plumbing system that rises up to the roof, or connects laterally to a pipe that runs to the roof. If this is blocked, a flushing action will suck water out of the trap (sink traps too) to satisfy the demand for air.
You can use a flashlight and look down the vent from the roof and look for a bird’s nest, or rodents, etc. If you have another toilet on the opposite side of the wall, have someone flush it while watching the water level of the first toilet. Look for the water to move when the first toilet is flushed. If it does, you probably need to clear the vent.