First of all, I'd like to mention that I do not use the garage drain for anything. I don't wash my cars in my garage, nor do I ever pour anything down this drain. The most liquid that has went down it since I've owned this house (1 1/2 years, 50 year old house) was probably the water that consolidated from using AC in my vehicles that I park inside.

I seem to have some sort of a back up in my garage, as I've noticed a nasty smelling (not sure if it's sewage or not) liquid and some black soot-like substance backing up. My drain is in the center of the garage and I am not sure where it drains to.

I let the liquid sit for a couple of days to see if it would drain and I found that it stayed at exactly the same level. Some of it I assume evaporated and was replaced with additional liquid from the drain, but thought nothing of it. I mopped up most if not all of the liquid and I thought the problem was mostly solved.

However, today I returned to see the same, nasty smelling liquid had returned to almost the exact same level and quantity that was previously there. Questions/thoughts/comments? Some initial research has me believe that this drain could be going anywhere from the sewers, to a pit under/beside my house, to essentially nowhere, or even into a storm drain... Why would this be backing up into my garage, unless it could be linked to other pipes in my house?

What's interesting is, regardless of doing laundry, taking showers, and flushing toilets the level doesn't seem to rise or fall much at all, and when I cleaned it up it was about 2 1/2 gallons of liquid (1/2 of a 5 gallon bucket). This makes me think that it's not related to the water heading outbound from the rest of the house.

I have a back up in my garage drain. I mopped it up and today I returned to see the same, nasty smelling liquid had returned to almost the exact same level and quantity that was previously there. Questions/thoughts/comments? Some initial research says that it is linked into the kitchen, and use of the kitchen is what backs it up. It then Ys to the main, and the main was tested as good to the road.

I was told by one plumber that it's probably a crushed pipe seeing as I and he was unable to snake it. Should I attempt to bust the cement up and get to the trap and check it out myself? What is the level of experience needed for that?