Convert powder room to master bath

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Michael Ardai

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My niece decided that since I helped with the electrical work on her new addition, I can do plumbing as well...
On the second floor, she had a powder room (toilet and tiny corner sink). The drain is a 3" pipe down to the basement with no other connections. Vent was a 1.5" pipe thru the roof (yes, I know it should be 2"). She is converting it to a master bath; framing is all done...

The bathroom is 7'3 x 18'4. The toilet will stay where it is, but of course the piping will have to be changed to allow for 2" vent and 2" drain from the rest of the fixtures. Basic room layout is shown below. I have full access to the attic void above, so I can easily dry vent and tie the vents together there before going thru the roof. I may need to run two vents through the roof to get to the area of the 3" pipe to the septic.

bathroom_floorplan.png

How does this look for a basic drain and vent scheme? Once I figure out the basics, I will tackle figuring out the correct fittings.
dwv_piping.png


To top it off, the drains must fit in a 2x8 joist bay or 2x4 walls. I may have a few extra inches below the floor where the stack is since that is in the boxed in soffits above the kitchen cabinet but that doesn't give me much space. I am not sure how the P-traps for the shower and tub will fit given the slope from the tub to the stack. The walls on the second floor don't line up with the walls below (but fortunately don't line up with floor joists either, and the joists go left-to-right in the drawings above).
Thanks for the help.
/mike
 

Reach4

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WC and shower need a vent, which must be done before the laundry waste joins the toilet waste. If you feed the laundry waste last, you could use fewer vents, because you would be wet venting. Only bathroom stuff in a horizontal wet vent.
 

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Michael Ardai

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WC and shower need a vent, which must be done before the laundry waste joins the toilet waste. If you feed the laundry waste last, you could use fewer vents, because you would be wet venting. Only bathroom stuff in a horizontal wet vent.
Thanks. That's a lot cleaner.

Also, this is in NH.
/mike
 

Reach4

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Also, this is in NH.
IPC makes things easier, or at least gives access to a code more are familiar with.

What path distance from the output of the tub trap U to the lavatory drainage joining? If under 8 ft, the light-green vent is not needed.

For laundry standpipe, you can run the output of the trap at least 4 inches to what would usually be the top port of a santee on its back. The side port would connect up to the vent. The usual bottom would connect to a 2 inch pipe to continue horizontally to join in after the toilet. After the vent, the slope can be equal to or greater than 1/4 inch per foot. Some codes require a combo for that venting, but IPC is more permissive on this point.
 
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Michael Ardai

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dwv fittings.png
I am just at the edge of 8' but it's easy for me to add the vent for the tub, so I will do so rather than worry about inches.

This is the plan with the fittings. I am not sure if the fitting from the tub to vent should be a sani-t or wye. I may change the run from the tub trap to the vent fitting to 1.5" to help with the total slope from the tub to the vertical run to the basement fitting in a floor joist bay.

/mike
 
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