I am finishing my basement and I am not sure where I can tap the drain pipe into. Below is a pic of the wall where I will be putting the sink. On the right is the 3in main drain stack for the house and 33in to the left of that is a vent stack coming from the cement. I will be putting the sink 16in to the left of the vent stack. I have followed both pipes and all waste water goes through the 3in sack and the 2in vent stack is used for venting only. (from what I can tell)
Where should I connect the drain for the sink? Do I run a line to the 3in main stack and vent it to the 2in vent stack or should I connect the drain to the vent stack and re-vent it?
And what size of pipe should I use for the drain, 2in or 1 1/2.

Thanks in advance for the advice.

Hi Netwrkguy:

You want to install a 2"x1.5" sanitary tee fitting into the 2" pipe as indicated in my drawing below.

Here, you will be WET VENTING the other fixtures using the lavatory vent. This is obviously what was intended or the lavatory pipe would only be 1.5"... ;)

Lavatory pipe should stub out of the wall 1.5" pipe size. If installing a pedestal, let me know as I have a little more info. That could help reduce frustrations later when installing the finish plumbing.

It will also be a good idea to install a 2" dandy cleanout (see picture below) just below the sanitary tee fitting. Face the cleanout toward the water heater but at an angle that will let you use it... just in case the shower/tub or sink drain clogs up in the future.

Let me know if you have any questions...

MARK

I am not installing a pedestal sink, my wife likes the contemporary style sinks so I will be installing one of those. She has been going back and forth between two different ones and since it is time for me to start roughing in the plumbing it is time for her to choose one and stick with it. :D
Is it because it is such a short run that I can get away without reventing the pipe?
Also one of the sinks that she is looking at has the bowl on top of the cabinet, it does not seem to have an air hole that you usually find on the more traditional sinks, If I go with that type of sink would that change whether I should revent? My assumption is that since the air hole helps draining by introducing air into the system if you take that away from the sink then the air needs to come from somewhere else right?
Here is and example of the one of the sinks she is looking at.

You don't have to revent because the pipe you are cutting into is a drain and a vent!

The 2" pipe is the drain and vent for the lavatory AND it is a vent for the toilet and shower but it is considered a WET VENT because the sink water also drains down the vent. The concept here is that..most likely..you won't be using the toilet and the sink or the shower at the same time....so they decided that you could use the lavatory vent as the vent for all the bathroom fixtures as long as it is piped correctly underground AND the lavatory drain/vent is run full size 2" until it connects into another 2" vent. What is important to distinguish is fact that a lavatory vent only requires an 1.5" vent but that toilet needs a 2" vent minimum...hence the increase from 1.5" vent to 2" vent in this case.

Anyway, if you cut into pipe as directed all your fixtures will be properly vented.

In terms of the vessel sink you posted... some have the overflow hole and some don't. If yours doesn't have the overflow hole then you will want to purchase a PUSH BUTTON, UMBRELLA, or a FLIP TOP (pics. #1,2, and 3 respectively) type of vessel sink drain assembly. Stay away from the grid style drains (pic. #4)... they don't work well with these.

Good luck!

Sweet, thanks for the explanation.