Whenever I get a clog in my main sewer pipe beneath the basement floor, water comes up through the floor at numerous random locations along the path of the pipe and at the penetrations where the pipes from the house enter the floor. One of these penetrations has a massive wad of what appears to be hydraulic cement around its base, so I'm assuming this problem is not new.

My guess is that the waste line is clay tile, and it is leaking at the seams whenever the water gets backed up. The house was built in 1922 (NE Ohio)... is my "clay tile" theory likely?

I know there are jackhammers in my near future, but before I get into that I'd like to know what the common plumbing practices of that era were, so I know what to expect.

Thanks in advance for any input!