Cabin DWV Rough In - On the Right Track?

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Jan 11, 2021
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Since July I've been self-building a 500sqft cabin which has been a perfect way to keep busy and away from others. It has been an incredible learning experience and so rewarding to work with my hands (I am stuck on a computer all day for my day job so this is a welcome change). I got things weathered in before snow, and am now working on adding the utilities over the winter months. I really enjoy learning and doing these things myself, but am outsourcing the electrical and propane hookups for insurance reasons.

The plumbing I would like to do myself and have been reading up on what I need and pieced together knowledge from the National Plumbing Code of Canada, various books, websites, and this forum which have all helped me get a basic understanding of how to rough in my drain, waste, and vent piping.

I'm hoping to get some feedback on the design I came up with and understand 2 main things:
1) Is there anything here that is WRONG?
2) Is there anything I can do to make this more efficient without sacrificing function?

The cabin is on a pier and beam foundation and I have pretty good access underneath. The kitchen and bathroom are back to back so all the plumbing is concentrated within a small area. There's a loft above and I'm trying to avoid putting plumbing in the exterior walls where possible. We're also pretty remote so we'll be using solar on the south roof so I am trying to keep the stack vent in the corner so it's out of the way as much as possible.

Pic 1 is the floor plan to show where the fixtures and non-load-bearing 2x4 wall is located

The small closet beside the stacked washer/dryer will serve as a utility closet housing the HRV/ERV, tankless propane hot water heater, well control box, pressure tank, and hopefully have a little bit of room left for some storage.

Pic 2 is a SketchUp drawing of the DWV rough in that I came up with. I am not the best with this software so I can't figure out how to change the piping sizes without starting from scratch but the toilet arm and waste pipe below the floor would all be 3" as well as the main stack vent up thru the roof.
I put the vents up thru the loft floor joists since I am able to bore holes of sufficient diameter in those 2x12s for the horizontal connections, but not in the 2x6 exterior wall studs. The kitchen piping I have kept just outside of the wall and the trap arm will end up behind base cabinets and the stack portion would be in the utility closet.

Pic 3 is another SketchUp view from below.

There is also a 4ply beam below the floor joists which prevents me from going straight down thru the sill. I couldn't figure out how to sketch this with a 45 degree bend so there are 2 90s instead. I was intending to do a 45 from below the sill to use less fittings and smooth things out.

So, am I on the right track here? Anything wrong? Anything I can improve?

Thanks in advance for any feedback!