Our tooilet has been acting funny for about 6 months. THe bowl fills up with each flush and then slowly drains. We had one plumming company come out and they augered the drain twice. The toilet worked for a few days then started acting up again. After they came out the second time, it stopped working that day. My father and I tried to check the vent pipe. We ran water down the pipe and got nothing. A second plummer came out and suggested replacing the stool itself. We pulled off the old stool and put the new on. Same kind of flush problem. We used a hand auger and found roots in the drain. The second plummer came out and augered the drain. After replacing the stool, the toilet flushed the same way. The plummer said something was syphoning the water out of the bowl put had no idea what it could be. Please help me.