smell
 

Just purchased a 2007 Windsport, had gray tank smell inside coach while camping. Found sinks with Pro Vents, tape them closed to stop coach smell besides using gray water treatment. Will this create a problem taping the Pro Vents? Also have roof vents so I beliveve this would not create a problem. Don't quite understand the need for Pro Vents.

The air admittance valves are used when there is no roof vent close by.
They keep the water in the trap from being sucked out when you dump. They are inexpensive and usually easy to replace. They unscrew and are usually hand tight.

What's wrong with the traps being sucked out? The roof vents are withing two feet of the sink.

That would allow sewer smell/gasses into the RV. That's why the 'trap' was invented in the first place. Perhaps if you ran some water into the drains after you dumped - or replace the valves you've blocked off with new ones. I'm guessing they aren't all that expensive.