I am remodeling a home. The home was built circa 1950’s (mere guess). The walls were mesh with apx 2” of concrete…it was built like a freakin’ bunker. I tell you this for a reason…chances are great that this home’s plumbing has not been updated or modified meaning what I will describe is how it was built. Further, this makes me think the problem I “believe” I have may not be one at all because how could this house have existed this way. OK. I have 1 bath on the main level. The toilet has a main stack downward (drain A) and goes directly out to the main sewage line and the same stack continues upward through the roof (vent). A “t” comes from it at about waist height, runs horizontal maybe 5 feet and is capped at the end. There are 2 vertical pipes going downward- 1 (Drain is the sink drain and the other one (Drain C) is not attached to anything in the bath room. Both drain downward toward the basement. All of those pipes (A,B and C) are black/cast iron. There is a 4th line (Pipe D) that is NOT attached at all to the prior lines. It is not cast iron but galvanized. This “solo line” simply comes up through the floor and is capped (PIN THIS).

There is an an ejector pit in the basement directly below the bath. There I can see the toilet stack go out the main line. FINE I also see the ejector pit is plumbed to pump out the same main line. FINE. The vent for the ejector pit is where things get weird. The ejector vent is tied into a line that veers right and ultimately ties to the “solo line (PIPE 4)” noted above. That solo line is capped in the bathroom upward and runs downward to and through the basement floor. It ties into two things in the basement- the ejector vent line (at above 4 feet from the basement floor) and a basement sink line at maybe 6” from the basement floor. So the ejector pit “vent” line is above the bathroom basement drain line. Chances are they both use this vent line. The problem is the line is CAPPED in the bathroom. It leads nowhere. Remember I mentioned this house has not been remodeled. This means the home was intended to work this way but how could it? How can a vent be a vent with a cap on it? Seems that line should continue through the attic and out the roof?