First off, this is my first post here and I wanted to thank the countless kind and knowledgeable folk who have answered all the questions over the years. I can't tell you how helpful this forum has been for me while I remodel a house on my own.
Secondly, my sincerest apologies for the crude diagram below!
The drawing below pretty much sums up my confusion. The kitchen sink drain runs horizonal for a bit, tees off and drains below the floor into the basement and vents up through the second floor where it eventually meets the main stack as it exits the roof. But that vent line ALSO goes back down through the first floor where it attaches to the 3" main sewer line as part of a sanitary tee with a 1.5" inlet that's connected to a toilet. WHY? No other fixtures drain or vent on any of that pipe. All of this serves only the kitchen sink. Please explain why it attaches to the main line again. It seems to my fairly unknowledgeable brain that there's no need for the vent line to re-attach to the main drain line.
Thanks!
Secondly, my sincerest apologies for the crude diagram below!
The drawing below pretty much sums up my confusion. The kitchen sink drain runs horizonal for a bit, tees off and drains below the floor into the basement and vents up through the second floor where it eventually meets the main stack as it exits the roof. But that vent line ALSO goes back down through the first floor where it attaches to the 3" main sewer line as part of a sanitary tee with a 1.5" inlet that's connected to a toilet. WHY? No other fixtures drain or vent on any of that pipe. All of this serves only the kitchen sink. Please explain why it attaches to the main line again. It seems to my fairly unknowledgeable brain that there's no need for the vent line to re-attach to the main drain line.
Thanks!
