Does their house smell cause they use the toilet???
RV's are self contained.
12V DC power for lights, water pump
Propane for cooking, fridge cooling, furnace
Fresh water tank to supply drinking, washing & service water
Sinks/showers and toilet for using
Waste water holding tanks
Sinks/showers have 'P' traps (just like houses) that hold water in trap and provide a vapor barrier from grey waste water tank
Toilet (unlike house toilet) doesn't have a built in 'P' trap because it is a gravity flush toilet BUT is designed to HOLD WATER in the toilet bowl (just like house toilet does) and provide a vapor barrier to black waste water tank
Wast water tanks (black & grey) have vent lines to provide a means of relieving pressure build up and allowing odors out above roof line.
RVs are just mini houses on wheels.
Use it, enjoy it--------GO CAMPING!