I just moved into a house we recently purchased. In the remodeled basement is
the laundry area. The original washing machine drain, which is in concrete
block wall, has been eliminated and another drainage system installed on the
outside of wall with its own vent. It isnt tied into the septic. The
original one is. A couple of says after moving in, we started getting the
smell of septic gas. I narrowed it down to the laundry area. I located the
original drain line and thought it was probably covered over and not sealed. I
was right. They had cover the whole area around the top of the pipe with
insulating foam. I removed the foam and there was no seal on the pipe. I used
an expansion plug and sealed it. It seemed to stop the odor in that area. Next
day, I had been away from the house for a while and when I walked in I could
smell the odor in the house. Im thinking there is a problem below the top
of the pipe which caused the previous owners to stop using it. They said they
had the system smoke tested and didnt find a problem. Now, my question.
Would it harm anything to force a ball Id foul down the pipe to about floor
level and fill the pipe with concrete? I think the crack or break in the pipe
is allowing gases to deep into the walls way below where I could cap it.

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