Help with vent situation in bath remodel

I have a bathroom going in and I'm having a bit of a problem getting a handle on venting things properly.

The black line is the outside sewer. There was a bunch of crap there - schedule 20 to clay to iron all wrapped with concrete. One good blow from a sledge - All gone now. I'll post a pic if anyone would enjoy seeing a superior hack job.

One of the constrictions is that there is not a lot of "fall" between the bathroom floor and that 4" connection - maybe 15"~18" tops. In fact, the dirt right under the floor is barely 6" below the 2 x 4 floor joists, so digging is involved anyway LOL. We just had the house lifted and leveled - the clearance was zero back there.

About all I can come up with right now is to come out of the pot with a 4 to 3 closet bend to a 3" sanitary T. The bottom of the T would go down and out under the house skirt to the 4" outside. The other side of the T would run 3" under the sink, then 90 towards the tub. I'd come up out of the 3" with a 2" up the short piece of interior wall behind the sink to drain/vent the sink. Then run 2" out of the tail end of the 90 over under the tub, then vent the tub up the closet wall or in the dead space behind the tub. Finally, I'd tie the tub/sink vents together in the attic, then out of the roof.

My current idea seems rather Rube Goldberg and I'm open to suggestions. We're still in the wrecking stage, so I have a bit of time to think it over. The walls around the pot are exterior and I want to stay out of them because they need insulation and are only 2 x 4. Also, I just beat a giant piece of 4" iron vent off the house (it ran in front of the window - really) and I'd like to keep it clean out there if possible. The house is on piers, so I have some flexibility in that corner, but not much.

PS - the whole house is Quest and I plan to cut the 3/4" runs that come in under the floor and go back with PVC. I believe there is one local hardware store that still carries Quest type fittings but I'd appreciate a source if I can't turn up something local.

Thanks in advance for any input.

pipes

WE do not know the dimensions, or the underfloor configuration, but one way might be to run the 3" pipe behind the lavatory, with a 3x3x3x2 sanitary tee for the toilet turned to face the location of the toilet's outlet closet bend, and then run from the 2" inlet to the tub trap, assuming it is within the trap to vent distance for your code.

Thanks - did forget the dimensions. The room is 6' x 7 1/2' with a 24" door.

That does sound like a better idea. I can make the underfloor dimensions do what I want - aside from the bit of Qest under there, there is just a bunch of iron abandoned in place. Between the sawsall and a shovel, I can make it work. Bonus item - I'll have a good pile of 1" copper drain pipe to recycle. That'll buy dinner.

Codes - we don' need no stinkin' codes. Actually, it'll be Texas state stuff. The town is about 2500 and probably has codes but we don't have any inspectors, permit process, etc. When I rewired the house after we moved in, I called the electric company and told them I needed to pull the meter for a bit. The response was "don't kill yourself, call us when you're done." When I built the garage, I called about a permit and the city manager said "Thanks for the heads up but we don't care as long as it looks decent."

Codes aside, I want to get it done correctly so it's safe, everything works well and I don't have to go back down and tinker on it.

Revised:

A sample of what was:

Revised:


I understand from reading other posts that the vent by the tub will have to be moved such that the vent pipe comes up vertical or at least rises at a 45. That'll take some more scheming to figure out pipe layout to accommodate the tub trap connection.

Revised yet again


How much room I have to work with:

Try again - can't use the toilet riser as a stack. Also had to move things around to get away from floor beams, etc.