Can a horizontal section of vent drop down if both sides drain to the sewer?

[Brandon Wilson]

I moved my walk-out basement half bath from the front of the house to the rear, the new bathroom serves a toilet, shower and sink. I would like to use the existing 2 inch vent at the front of the house that now serves NO fixtures (it served the original toilet and sink, now removed).

I would like to run the new two inch vent horizontally from the rear of the house to the front in the joist space (about 30 feet), then drop a few inches below the joists to tie into the old 2 inch vertical vent. We use IPC (~2015)

The old 2 inch vent goes to the roof, and also down to the main drain pipe that leaves the house, this 2 inch is separate from the 3 inch main stack. Would this be feasible considering both sides drain to sewer?

Appreciate the help.

 

[Reach4]

IPC is OK with the vent sloped so that one slopes one way, and the other part slopes the other way.

If that pipe section is true horizontal in the mathematical sense, then it is not allowed, tho it probably would not hurt in practice.

 

[Sponsor]

 

[Brandon Wilson]

I would slope the 30 foot section back towards the fixtures to drain there at the appropriate drop per distance, the small 3-4 foot horizontal section at the front would slope to drain into the sewer at the front of the house using the old vent's connection.

Thank you for the input!