I had this same problem when I first moved into this home. Thing is I did some reading and I thought it was roots. I called a plumber to come out to my home. I told him that I thought the problem my be roots and to go as far in to the pipe as he could to CLEAR it for sure. What did he do? he got out a power snake and went a little bit into the drain. Did this fix the problem? Yes for about 7 monthes. Now it's back to where it was. Bottom line is when you want something done right do it yourself. This jerk had one thing on his mind and that was taking my money. They hope you will be dumb and just call there asses back time and time again so they can do there half ass work and leave in 10 minutes. FOr any plumbers reading this, don't think people who don't do what you do, don't realize that SOME of you do crap work. I told this guy I didn't want there to be another problem because of him not going farther into the pipe. He said... "oh it's not roots, you just had a "small clog" I believed him cause after all what do I know right? Well why the hell do I have the same problem only 7 monthes latter? Give me a break!! Micah.