I'm installing a 2nd bathroom back to back with the present bathroom. I have a toilet drain and wish to connect a 2nd toilet to it as well as a new shower drain. The 2nd toilet will be 3 feet from the present toilet and the new shower drain will be 5 feet from the present toilet. Anything special I need to do? I plan on just putting a new tee where the present toilet is and connecting the 2nd toilet and new shower drain to it.

Just make sure you vent the shower.

Hi Ted,

"Anything special I need to do? I plan on just putting a new tee where the present toilet is and connecting the 2nd toilet and new shower drain to it"

Just one hitch. You may not discharge a major fixture,m(your toilet) past a unvented minor one,(your shower). Also every fixture except floor drains that have a trap MUST have a separate vent or be wet vented.
You must run a vent for the shower. Now if you were to install a lavatory you could then connect the lavatory drain to the toilet drain and run a vent or AAV off the top of the tee that picks up the lavatory. You may then connect the shoewer drain to the lavatory drain line and the shower will be wet vented. Your call, but one way or another a vent has to be installed.
Good luck, Tom

Do I understand this correctly? The shower drain will connect to the lavatory (sink), which will be vented, and then the lavatory drain will connect to the tee that the 2nd toilet connects to the present toilet.

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Originally Posted by tedles

Do I understand this correctly? The shower drain will connect to the lavatory (sink), which will be vented, and then the lavatory drain will connect to the tee that the 2nd toilet connects to the present toilet.

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No, The vent will run off the top of the 2X1/12" drainage tee that will stubout to pick up the lavatory. The lavatory drain can connect any where in the 2nd. Toilet drain line. The shower will then connect any where in the lavatory drain line and be wet vented by it Regards, Tom

Yea, make sure your shower drain is 2" though, The lav can be as small as 1-1/4 however I'd suggest 1-1/2, And use a AAV (air admittance valve) under the vanity on the lav drain

"the lav can be as small as 1-1/4 however i'd suggest 1-1/2,. and use a AAV (air admittance valve) under the vanity on the lav drain"

As much as I hate to disagree with another expert, we do not use drain lines under 2" any more, especially horizontal drains that carry hair and grease that mats together. The larger size pipe will not clog up like the smaller lines do. While it's true the lavatory drain and trap is 1 1/4" the pick up tee in the wall is a 2X2X1/12" tee, The AAV or outside vent connects on top of the tee in the wall. Cheers, Tom