Hi Scrupulous,
Thanks for the positive comment.
Those are good suggestions but if I understand them correctly, here is why it would not work.
Without the second trap at the UTA, Sewage gasses from the rest of the system could re-enter the occupied space through the toilets vent/vents.
Even if you added a second trap downstream(which I am almost positive is a code violation), anytime the dishwasher, washing machine, tub, shower, sink, or even another toilet flushing, not only would you hear it though the toilet, you would smell the various odors.
Also by adding the second trap you have eliminated the rationality somewhat of eliminating the first one at the UTA.
If you kept the fan on continuously to compensate for the odor removal, you would still have the noise coming from the toilet issue only this time you’re also hearing the fan. Not to mention the added cost and extra operational wear of the fan.
Also my idea is not limited to homes only. Imagine the above issues in a multi-floor system, restaurants, factories, stores/malls, ect..
By code, vents have to be within a few feet (5 feet max I believe) of all traps so there are usually a few at minimum on any given house. If you had the fan on the vent line, it would draw air through the other vents as well thus reducing the cfm flow at the toilet therefore reducing the performance of odor removal at the toilet.
If you tied all the vents together to a main/master vent, it could create issues with the whole house system because the vent system needs to "breath" in and out. Also it is possible to evaporate or suck the other traps dry, especially if not used frequently.
And with all the additional piping to tie the vents together, you have spent more than what the original design had.
Those are a few reasons that I can think of now, I hope that I under stood you correctly and that my explanations make sense. I appreciate the responses you had as it allows me to re-think my idea to make sure I am on the right track.
Thanks again Scrupulous.
http://www.bettertoilet.com