I'm installing a double bowl sink in existing single story building on an outside block wall. The septic tank drain is right outside the wall but I'm concerned about venting. There is no way to vent directly up from the sink, its on a cement slab & the waste will go directly out the block wall. I'm not hot to put holes in the roof. I couldn't go straight up with a vent anyway but there is an interior frame wall about 4 feet to one side that reaches the ceiling. I'd prefer an air valve but I don't think they will work in this case.

Isn't there a way to vent directly on the outside wall with a pipe towards the roof?
I mean : instead of outside a bend down to the tank, put a T piece there with on top the vent pipe to the roof.
Do you have to go through the roof? Can't you go around the roof using a couple of bends?
Just suggestions... I am not claiming to be an expert. Just an active do-it-yourself-er ! :)

Success !

Install "ProVent" aka Automatic In-line Vent. It installs between P-Trap and before pipe enters your wall. Home Depot sells them for $2.99. Just bought one today...

Don't have picture of the vent - but give it few moments: once Tom reads this post, he'll post the pic.. . :D

Install "ProVent" aka Automatic In-line Vent. It installs between P-Trap and before pipe enters your wall. Home Depot sells them for $2.99. Just bought one today....

Don't have picture of the vent - but give it few moments: once Tom reads this post, he'll post the pic. ......:D
Milo nailed it. I would install a AAV,(Air Admittance Vent ,see image) but get a better one then the $2.99 special. A Studor Vent, (see image) comes to mind. Good luck, Tom

Milo nailed it. I would install a AAV,(Air Admittance Vent ,see image) but get a better one then the $2.99 special. A Studor Vent, (see image) comes to mind. Good luck, Tom

I was looking at this option but wasn't sure that this vent could be used as the only vent for the sink. It would make my life a whole lot easier than venting through the roof. And an exterior vent stack is an unattractive choice. The web site for Lowe's shows the Studor Vent @ $22.36 but Home Depots site can't locate an AAV.

Thanks to everyone for the help