Hi Rikdiy and Welcome to The Plumbing Page. At AskMeHelpDesk.com. To answer your question, Not if wet vents are allowed in your area. Your toilet will be wet vented by the lavatory roof vent. Good luck, Tom

Yes, the toilet needs a vent. All depending on how the sink drain ties into the toilet drain, it may serve as both the toilet vent and sink drain if wet venting is allowed in your area. Do know however, that this is an easy one for a diy'er to mess up. There is a standard procedure here, but must be done just right. Only one way to really wet vent this correctly, and a whole bunch of ways to do it incorrectly.

Ya got dad concerned. Let me give you a example of a bathroom wet vent,(see image). If the toilet's between the lav and the pit I can't imagine a plumber doing anything but connecting the lav downstream from the toilet and connecting to the toilet drain and that, my friend, is a wet vent. Good luck, Tom

Correct you are Tom. And your pic is dead on. Only thing I worry about is them not tieing the sink and shower drian in downstream of the toilet. To many times I see people drop the toilet into a tee, and the sink and shower into the backside of the tee. This is no longer considered downstream, but upstream, leaving the toilet (at least by current codes) unvented.

Hey rikedry. Can you show us how your drainage's configured? Does the lavatory wye into the toilet main downstream from the toilet? Back to you, Tom

Hey rikedry. Can you show us how your drainage's configured? Does the lavatory wye into the toilet main downstream from the toilet? Back to you, Tom

I haven`t started the drainage lay out yet , was doing the research first so that I do it correct the first time. So Im open to suggestions. Your answers to my questions are very helpful and the diagram you posted too. I was going to lay it out the same as the diagram minus the shower , I will only be doing a half bath . Haven't cut the concrete yet so I`ll lay it out as shown in your pic using a y to connect it before the toilet. Again your insight is apprecated and I thank you

Keep us informed of your progress. And if we can help we're as close as a click. Good luck, Tom

Yep, if you do as Tom drew up, you will be just fine. It doesn't hurt to roll the toilet vent/sink drian wye above centerline. Most areas actually require this. Some don't, because as long as you are using the toilet vent as a sink drain, the sink will keep the toilet vent clear. May want to check with local authority on this just to make sure you get it all up to specs. You always want to get the "under concrete" stuff done right the first time. Keep us posted. Lee.

Yep, if you do as Tom drew up, you will be just fine. It doesnt hurt to roll the toilet vent/sink drian wye above centerline. Most areas actually require this. Some dont, because as long as you are using the toilet vent as a sink drain, the sink will keep the toilet vent clear. May want to check with local authority on this just to make sure you get it all up to specs. You always want to get the "under concrete" stuff done right the first time. Keep us posted. Lee.

I will keep you guys informed on my progress, will probably start cutting concrete next week. Again thank you guys for your help. Erik