Purchased a Drake toilet 2 years ago to replace my old basement unit and I've had an on again and off again problem with this thing ever since. When the thing works, it flushes strong and hard with no problems - great!! But at least once or twice a month before using the toilet I will notice that the water level in the bowl itself is way down near the base (throat) of the bowl, not even close to the normal water level in the bowl that it should be at??? and when I flush it there is a surge of water that actually backflushes into the bowl filling it to almost the very top. It then takes 4-6 hrs, sometimes overnight, for the water level to slowly go down. When the water level in the bowl does go down it again levels off to the base of the bowl. The toilet can't be "used" at this time. I then flush it again each time (days) that it does this until it finally flushes normally (I don't know why) and fills back up to the normal water level in the bowl itself. It then can be "used" without any problems until I notice the low water level in the bowl again and the process starts all over again. I give up-is it the toilet or is the waste pipe itself at fault, a clog or venting problem!!!??? Sorry for the long thread and any help or advice would be greatly appreciated.