I recently built a 40x60 steel building with 14ft. sidewalls on some land a bought. The house will come next. I framed a bathroom that is 7ft tall and made it where i can use the top of the bathroom for storage. The bathroom has a shower, sink, and toilet. It drains to a private undergound septic system. I was wondering if I could use just an air admittance valve for the drain and vent system to get away from going through the roof with a vent pipe. I had a local plumber say it was okay, but i am still not sure. Also, I have no code restrictions where I am building. Any advice on the matter would be appreciated and thankyou in advance.
The septic needs to "breath" both ways. About the only thing your valve will do is to keep from vacuuming a trap dry. (gurgling at a sink or tub) The septic builds up gasses that need to go somewhere, therefore the vent. So my answer is no. It's not my choice of ways to do things but, you could go through the wall and up the side of the building with a vent pipe.