My plumber at the cottage bailed on me and didn't install a drain for my master onsuite sink, so i need to rough in the drain to the crawlspace underneath.
My vent stack is a 4" i believe and my drains from the shower and toilet are 2" and both run to the 4" and then down to the septic. When the vent stack goes into the crawlspace theres only about a foot showing and its already got 2 connections from the shower/toilet, can i tee off my drain into the shower drain close to the connection to the vent stack? or is that not allowed because theres no air/vent behind the shower drain?
I guess i could join it into the sloped drain on the way to the septic?