: My toliets continue to overflow. We have checked the plumbing for both bathrooms to the septic tank for cloggs. We have dugged new tail lines. We have checked the tank to the tail lines pipes. We have checked the breather pipes, we have replaced the toliets with new ones. We have checked the dowm flow : of the plumbing. What is happening and how do we fix it?if all these things have been done correctly you should have a problem, but since you do, the next thing I would look at is the pipe comming into septic tank,is it above water level in septic tank as it should be? if it is and the toilets still overflow then the septic tank and field are eliminated as cause of problem. the next thing I would check is the main line again. could be a sludge build up that snakes (sewer rod)will pass through without dislodgeing. a drain line jetter would solve this. good luck