Originally Posted by uplumb
Re-read the instructions.. they clearly state in several spots NOT to tap into the bottom of an existing horizontal drain line..
With that system, you do not need to tap into an existing vent..
*** Please keep in mind that the system you are installing is a pressurized system.. if your connections and supports are not correctly fastened, you will have a large mess on your hands..
I didn't actually mean that I would tie in to the "bottom" of the horizontal drain line. If I did that, all of the waste water would run down into the upflush toilet unit. What I meant is that I would tie in to the horizontal drain line at a low point in the horizontal run, but I would still use a wye connection that is pointing up and waste falls down into the horizontal line.
Then, further up on the horizontal run I was thinking of tying in the vent pipe since that horizontal run itself is vented. The only thing I don't like about that is the vent pipe will have to go down a bit at the end in order to tie into the top side of the main horizontal stack. I would think it would "work" though. No?