Waste line connections
Currently I have 1 toilet but am moving it a little and adding a 1/2 bath. I have a vertical waste line in basement 3" diameter. It is connected with a 1/4 bend to current toilet horizontal of about 5 feet. I am remodeling and have to move current toilet over by one floor joist. I was going to use either 2 wyes in vertical or combination wyes depending on how dimensions work out. I have read that wyes or combination wyes are not allowed in vertical waste stack. Is this correct? If so why is this?