Bought a new toilet and installed it. We opened the valve, the tank and the toilet bowel fill but then the water in the bowl slowly gets suctioned down into he sewer pipe. I have had 2 plumbers to my house. They say that the pipe is under water in a slab of concete and is not getting air (venting problem). I am confused because my old toilet worked.. They tell me that it is because it was a 3.6 gal per flush and it had enough pressure to create a vent. They said that the new toilets (energy saving) don't have enough pressure. The plumbers told me there is no way to fix this problem because breaking up the slab could cause my house to shift.. As you know 3.6 are outlawed.. and my old toilet is in the trash .. I need a black market toilet or a way to fix this. PLEASE HELP!!!