I am installing a new toilet in a new room (old room just converted from office to bathroom)I have no plumbing in the room but under the room, is all the plumbing for the rest of the house. I feel comfortable installing everything I just didn’t know if I HAD to vent the toilet drain or not. I know I have to with the sink, but if I don’t for the toilet I didn’t want to bother runnig the vent to the roof (it's a new roof)

Hi Ruidoso...

If you are planning on just installing a toilet and no sink then you will need to add a 2" vent to the drain line and run that up and out the roof as you suspected!

If adding a sink, then you can use the vent for the sink to act as a vent for the toilet as well. Here, you would install a 3"x2" wye fitting into toilet drain line, run 2" over to sink, pick up sink and then run a 2" vent off the sink line up and through to the roof...

Sorry, but seems either way you are going through that roof!

Let me know if need more information... ;)

MARK