Originally Posted by cmulvey
Normally drains are vented as they also are in your house. You'll probably see that one is above the bathroom(drain) and the other is in the proximity above your kitchen sink.
Your black and grey holding tanks are vented through those so the odors will be more likely dissipated better and not be noticed by you or your neighbors. Some RV's have the sink and shower drains connected to those vent pipes, others have an Air Admittance Vent (photo attached) under the sink or in the wall near the shower.
Check for a AAV under your sink(s) or behind the shower if you get a foul odor inside and cannot pinpoint it as these vents fail or stick occasionally .
Your fresh water holding tank is vented at the tank and doesn't require as large a vent.
Richard & Jill
2014 Flagstaff 832IKBS Classic Super Lite
2018 Silverado 1500 Crew Cab Z71 4WD All Star Edition
Camping since 1989
Car Shredder Op/Tech, Scrap Metal Recycling - retired
Everyone gets confused at some time, some are better at hiding it than others.