Bathroom Addition | Page 3 | Construction and DIY projects | Forums

Preliminary plumbing modeling. I will still have to combine the vents somewhere in the rafters. I know I can cut a hole in the top plate of the load bearing wall with the right parts from simpson but anyone know if I can cut through the ridge beam? I'm leaning towards roof trusses anyway for cost but just curious.

The water drains from the sinks and the shower come together before exiting through the cinder block wall (need to avoid dropping them too early for their path to the greywater holding tank) while the black water from the toilet will drop down to go under the footer. The vents of the shower and the black water join before going up through the non load bearing wall. I plan to combine all of the vents up top before sending them through the roof.

Apparently my response never posted. 

Would it help to raise where the black water vent and the gray water vents combine to above where the toilet is? This should warn of a clog by way of a backed up toilet long before the black water jumps the vent.

What would the benefit of that option be over the tying it in with the shower? I would have to go through the top plate of a load bearing wall so I thought that tying in with the shower would be easier from a logistics standpoint.

Sounds good. I'll rerun it like the photo below. Thank you for making the inquiry in my behalf 

As you noted with the low flow modern toilets, I may opt for 4" drainage all the way to the septic tank unless you see any concerns with that.