Studor Air Admittance Valve

This is the second one I have installed, and it doesn't work. I wish they did as I don't want to poke another hole in my roof, but it's a crappy solution to venting. This particular model doesn't work as it should at least for me. I had a master plumber tell me during our house construction that Studer valves might work for a short time, but they all fail. I really should have listened more as I think he's right. Just run the vent up and out and be done with vent problems. You can tell if you have a venting problem if your toilet "burps" after flushing.