Drain and vent plumbing for addition
Hello, folks. I'm not a plumber by trade, but I'm trying to learn the trade. On our addition, there will be a laundry room with a front load washer and a large utility sink. A 2" ABS drain/vent pipe is in the wall right behind and between where the two items will be.
For option a, I want to put a double sanitary tee on the main vent stack, about 14 inches off the slab, and then run the vent out of the top of it. Off of one side of the double san tee, I would run 2" ABS about 18 inches to first a p-trap, and then up to my standpipe for the washing machine (top will be at 36"). Off of the other side of the double san tee, I would run about 18" of 2" ABS horizontally, add a 90 degree elbow, and stub it out of the wall where my sink drain will be. This stub out for the sink drain would be located approximately 14" off the slab.
For option b, I would stack two sanitary tees, one on top of the other, starting at about a foot off the slab, and continue my vent out the top of the topmost san tee. Off the top san tee, I would run about 18" of 2" ABS horizontally, put a 90 degree elbow on it, and stub it out for my sink drain (about 14" off the slab). Out of the bottom san tee, I would run 18" of 2" ABS horizontally to a p-trap, and then hook that to my stand pipe for the washing machine. My question here is this: If this is even a good configuration, which device should be hooked up to which san tee (should the sink drain be on the top or bottom san tee, etc.)?
In my inexperienced opinion, the two devices (sink and washing machine) are close enough to the 2" main vent stack that additional venting wouldn't be necessary (like a vent pipe leading from the sink drain pipe, up a few feet, and then cutting over to the main vent stack).
If my explanations are confusing at all, I will gladly draw a picture of the layouts and upload it to photobucket. Thanks for any help that any of you can give me!