Just recently, the water in the toilet bowl has been sucked out down the pipes. Note the toilet reservoir does not empty, the standing water in the bowl is emptied as if it is being drawn out by a vacuum. This must have someting to do with the apaartment building that we live in. Does anyone know why this is happening and how to fix it? While it happens when other residents flush their toilets, it often seems to just happen by itelf without warning.
Thanks
MNM