I am installing a sink and toilet in my basement. Actually two sinks, one bar sink and one in the bathroom.
My questions are,
:)can I use the roughed in bathroom sink drain and tap into that for the bar sink. I am putting the bar right outside of the bath room wall so the drains are going to be farily close.
:)If I can do that, do I need two P traps, if I vent the system properly, then the bar sink P trap should not drain when the bathroom sink drains correct?
:)Also, in the bathroom and in the bar sink, how high should I start the drain off the floor to ensure proper flow? I think that I need a quarter of an inch pitch.
:)How would you recommed that I tie the two drains together?
:)For the rough in, I used copper tubing. The 90 degree with one end sealed. How can I test for leaks without first putting the drywall on and then the shutoff valves? If I put the shutoff valves now, before the drywall, I will have to cut huge holes in the dry wall to fit over the valves.

I apologize for asking soooo much.

1. You can use Double Sanitary Tee. See image. This way you will not end up with wet vent.
2. You will run single vent that will service both sinks. In your situation both sinks will have its own trap.
3. Start drain inlet at about 19" on center off of the floor.
4. Slope it at 1/4" per foot.
5. To test your installation for leaks you either insert SharkBite Cap, or solder on 1/2" cap which you will cut off after drywall is installed, or install 1/2" x 6" copper stub out with tapered end.

After studying the photo, I just thought of something. I did not mention that the roughed in drain is not in the center between the wall. It is like this, drain roughed in floor, bathroom sink drain and then the bar drain.
1 - drain in basement floor
2 - bathroom sink
3 - bar sink

Are you saying both sinks are to one side of the drain inlet ?

Can you post a photo ? Or Sketch ?

Here is the photo of the job so far
Drain is in the concrete floor
Rough in for bathroom sink in the middel
Rough in for the bar sink on the right hand side of picture.

John, is this (red arrow ) what you assume is the sink drain ?

No, it is the pipe up against the wall, I verified with the plumber who did this house when it was built. The red arrow is point to the toilet drain. The sink drain is to the left of the toilet drain up against the wall.

Sure, that's toilet inlet...

That pipe in the back and to the left of the toilet inlet is vent for the toilet. You should not connect to it. Drain for the sinks will have to be connected to the pipe on the right ( pipe with clean out). You will have to rework it.

Now, when I see the pic: I see the h/c stub-outs for sink . Where exactly is the bar sink going to be ? Please, explain...

What's that h/c plumbing all the way on the right ? Tub? Bar sink ?

Ok, thanks a bunch, the bar sink, is to the right of the rough in for the bathroom sink. I would put a red arrow but I don't know how you did that. Interesting because I could swear that the plumber who did the house said I could drain into that toilet air vent. If I need to cut into the big drain pipe with the clean out, that is going to be a big job. Shoot. I am going to have to study this one.

John, is this project being inspected ?

Bar sink
How would you recommend hooking that up. Boy cutting into that main pipe sure looks like it could be quite a project

Do you have any suggestions?

See the drawing. One inlet would go into 3" pipe, the bar sink drain would extend from 2" vertical drain. Drain inlet height should be around 19" high. Additionally, you will need vent for each sink. You could install AAV right behind each trap inside cabinets.

John, it is not such a big deal cutting into 3" vertical pipe. PVC is easy to work with and requires only basic tools and skills. We can lead you trough it...

Is this project being inspected ? AAV are not allowed in some places.

One thing that I noticed is the that the 2'' verticle pipe is up too high to tap into. Do I need to tap both drains into the 3' verticle?