Waste Water Backup Problem
I have a recurring waste line backup issue that I will do my best to explain. I would appreciate any suggestions as to potential causes of this problem.
Periodically, water backs up and overflows from the cleanout hole in the verticle stack in my basement (which carries waste water from the upper floors). This does not always happen, but when it does, it is usually after using the washing machine or dishwasher. It has also happened after someone has taken a long shower and a toilet was flushed during the shower.
There is also a toilet bowl in the baseement located about 8-10 feet from the stack (towards the front of the house). Waste water has also backed up from the toilet. On a couple of occassions, I've noticed a black sludge caked on the inside of the toilet. Sometimes the toilet works fine, but other times it does not flush. I've also at times noticed water bubbling after flushing the toilet.
There is another main cleanout about another 10-12 feet from the toilet, next to the front wall of the house. I've opened this to observe the flow of water to the sewer main. At times, the water appears to flow freely. Othertimes, it seems to sit there. I've also noticed it swirling at times, and, occassionally, it seems that some water may get sucked back into the house. Another troubling sign is that when I flush toilet paper down the basement toilet bowl (which is only 10-12 feet from the cleanout), I do not see the paper pass through from the cleanout.
I have snaked the main from the stack. I have also removed the basement toilet and spent a couple of hour snaking. Although a bunch of soap scum and grease was pushed through the pipe, it didn't solve the problem. I have also snaked the main running between the house and the sewer line and did not meet any resistance.
At this point, I am concerned that there is a crack or collapse in the pipe under my house running between the toilet bown and the front house cleanout (or possibly somewhere else). Any thoughts? Thanks!