well I found the vent... or what it they put in as a vent.. UGH!.. I found it under the insulation.. or should I say the stub of the pipe... it's been sucking air from the crawl space between the floors of our home ( old home 24 inches between floors. So that is WHY the system works. Oddly enough if it's quite near the vent for our bathroom so it will be easy to tap into. I just need to get to the big box store since the vent in the wall is HUGE... up on the thrid floor level it's at least 3 inches maybe more and my local place as much as I like them has almost no PVC parts. I am going to be kind and just decide that they forgot to hook up the vent and since the system worked not one ever thought about it but I am sure glad I found it now instead of after I got the new flooring in!