Venting

I am replacing a tub with a walk-in shower and struggling with finding a proper solution to vent the new 2" drain. From reading discussions in these forums I know the old drain was not ran properly, I will spare the details, but I would like some feedback on a couple possible options I have come up with to attempt to fix it properly. I don't think either is perfect, but my options are pretty limited without major destruction.

It is a second story bathroom, drain is a 3" PVC stack. I have a toilet and sink feeding into the 3" stack (each with their own 2" vent) and trying to add another 2" drain. My new shower drain will be located within about 16" from the 3" vertical stack. Here are the options I have come up with (picture included):

1. Connect the arm of my 2" P-trap directly into the 3" stack via san-T. This would be a wet vent situation with a toilet and sink upstream.

2. Add a dry vent before dropping into the stack. Problem is the vent will be a 90 elbow ontop of a San-T and have to run horizontal about 3' to the wall before going vertical. I know I can't tie into another vent until I get above the flood level of the other fixtures, but I wasn't sure about running the vent horizontal for a few feet. It would still be a few inches above the P-trap arm.

Link to drawing:
http://www.ddotsolutions.com/ddot/options.jpg

How far will the shower drain be from the stack?

About 16" from the shower drain to the stack.

One more, maybe dumb question. Does the drain have to dump straight into the p-trap. Reason being, my shower is actually over an overhang on the second story (directly below the drain is outside) I would rather the trap be moved over about 6 inches to reduce the risk of freezing. This is how it was done for the previous tub.

Are you going to tile this? Have you looked at the stuff that Schluter Systems makes? They've got a tileable shower pan made with the drain on one end specifically made for a tub replacement. Neat system. Check out www.schluter.com Also, once you've got the plumbing scoped out here, check out www.johnbridge.com for tiling help and the way to make a bulletproof tiled shower.

Thanks Jim. I was planning to do a cultured onyx shower:
http://www.onyxtop.com If you have any opinions on this, I would be interested, I have not ordered it yet.

I will give the tile a second thought; I think some of them look better.

Even with the drain on one end, I still have to run a new 2" drain, as the existing was only 1-1/2". The old drain made four 90 degree bends before making it to the stack and the vent took off horizontal. I am not wanting to do the same thing for my new shower because it will be more important that it drain properly. A center shower drain is actually closer to my stack, but further from an existing vent. Thanks for the reply.

Someone was saying that you aren't supposed to have more than one 90 degree turn without a cleanout otherwise you'll never be able to run a snake through it to clean it out if necessary. Not sure if it applies to this.

Another tileable system is by www.wedi.de Really neat system. I'm toying with one for my mother's house.

Schluter has a shower pan for a tub replacement that has the drain in the (normal) middle of it, too. That one has been around for awhile; the other one is new in the last month or so.

vent

We would really need a picture of the situation, or a drawing so we can be sure we are interpreting your description properly. There may even be an easier way, if we could see what you are working with.

Is there any way to vent the shower in one of the shower walls? Like HJ said, showing your floorplan and location of waste stack will help us get an answer for you.

Layout drawing

Here is a drawing of my existing layout. I am replacing the tub with a shower. Hope this helps.
http://www.ddotsolutions.com/ddot/b.jpg