I have new new modular cape that had the first floor plumbing complete, and the second floor stubbed, and want to know the right way to connect the second floor waste drain which was installed in the house, to the main waste drain.

The main waste drain comes up verically from the basement floor along the outside wall (where its connected to the sewer) and has all first floor waste lines draining into it. There is a vertical arm stubbed on this waste drain, which is capped about 1' from the basement ceiling (which is only insulated, not sheetrocked). The second floor waste drain is 8 feet from this drain (toward the center of the house and about 12" to the left, in between two joists. There is an existing pipe that goes from the main drain to the main stack.

looking up from the basement to the basement ceiling:

first floor drains
|
|main stack vent
|------------------------ <- joist
W======V..........O main waste connected to vent; second floor stub
|
O stubbed arm off main waste
|-------------------------- <- joist

So, I need to "simply" get from the second floor stub to the stubbed arm on the main waste drain.

I'd like to keep the pipes in the ceiling if at all possible. The joists are 2x12.

Can I use a 90 elblow to turn from the vertical second floor stub to the horizonal or do I need 45? Likewise, can I also use a 90 elblow to go from the horizontal into the stubbed arm or need 45? And I assume I need a cleanout near the second floor stub - also 45 or 90 angle?

|---------------------------
|... o <- what angles can I use to change from
|... / vertical to horizontal
| O---------------- <- clean out
|---------------------------
.. ^
and back from horizontal to vertical?

Hey Steve,

While I'm sure you have the lay out firmly in your head I need a diagram to understand it. I confuse real easy.
You speak of a of a stack vent. Does that mean the first floor fixtures are vented by it or do you have a separate vent stack for them? I hope they are vented by a separate vent stack because if they vent into the stack you wish to tie the second floor fixtures to then the venting system for the first floor will have to be reconfigured before you can discharge the second floor fixtures into it, However, while you may have to change the first floor vents you will be able to use it for the second floor vent. Good luck, Tom

The stack vent is the existing vent for the first floor fixtures. The second floor fixtures have their own stack vent.

The first floor plumbing is complete and inspected by the plumbing inspector.

The main waste pipe has a vertical stub that was insalled by the plumber to connect to the future (now present) second floor drain, that came with the house - just a 3" vertical pipe to drain the upstairs fixtures. This pipe now extends through the roof as the second floor vent, and the upstairs fixtures vent into that.

So, my only quandry at this point is how to tie the second floor drain into the main drain. I think I can do it with 45 bends, but wanted to be sure, and also check if I can use 90s if I have to.

"The stack vent is the existing vent for the first floor fixtures. The second floor fixtures have their own stack vent.
The first floor plumbing is complete and inspected by the plumbing inspector."

Just so we're on the same page a stack vent has discharge draining into it while a vent stack is dry and is used as a vent only.
Are you saying that you have two stack vents? One for downstairs and another for the upstairs rough? If so you're home free, if not then you have a problem.
It is always preferable to use long sweeps or 45's in a drainage system rather them 90's. Good luck, Tom